Research Note
Differentiation in Environmental
Treaty Making: Measuring Provisions
and How They Reshape the
Depth–Participation Dilemma
(cid:129)
Deborah Barros Leal Farias and Charles Roger*
Astratto
In this article we measure, describe, and demonstrate the importance of differential treat-
ment for developing countries in multilateral environmental agreements (MEAs). So far,
we argue, quantitative research on differentiation has been minimal due to data con-
straints and the complex nature of relevant provisions. In response, we offer a way of
relieving this constraint, exploiting the fact that MEAs with differentiation typically iden-
tify distinct sets of “developing country” parties. After describing the data collection pro-
cess, we show that differentiation is surprisingly uncommon, appearing in only 6 per cento
of MEAs, and disproportionately appears in larger, more recent agreements. We then test
a key conjecture about differentiation by revisiting the debate on the depth–participation
dilemma. We demonstrate, specifically, how it conditions this relationship. When MEAs
do not differentiate, greater depth reduces participation; when they do, the relationship is
reversed, making it possible to sustain high levels of both. This result helps to reconcile
conflicting findings in earlier studies and has important policy implications.
Differential treatment is a widely discussed feature of international environmental
agreements. It can be defined as a specific type of arrangement between states,
usually reflected in treaty provisions, that recognizes distinct sets of parties—
typically, “developed” and “developing” countries—and asymmetrically divides
* Deborah Barros Leal Farias’s research was supported by the University of New South Wales.
Charles Roger’s research was supported by the Institut Barcelona d’Estudis Internacionals and
the Beatriu de Pinós Programme (2018 BP 00276, AGAUR, Generalitat de Catalunya). For
their helpful comments and suggestions, we thank Jen Iris Allan, Peter Dauvergne, Yannis
Karagiannis, Jean-Frédéric Morin, Miriam Prys-Hansen, Sam Rowan, the GEP editors, and the
three anonymous reviewers. We also wish to thank Helmut Breitmeier and Ronald Mitchell for
providing assistance with their data.
Global Environmental Politics 23:1, Febbraio 2023, https://doi.org/10.1162/glep_a_00686
© 2022 by the Massachusetts Institute of Technology. Published under a Creative Commons Attribution 4.0
Internazionale (CC BY 4.0) licenza.
117
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118 (cid:129) Differentiation in Environmental Treaty Making
rights and responsibilities across them (Honkonen 2009; Rajamani 2006). It man-
ifests in different ways: as distinct obligations, as variable modes of implementa-
zione, and as targeted assistance (Rajamani 2006, 94). Yet, in each case, it represents
a departure from the more general principle of sovereign equality. Largely because
of this, specific instances have often been lightning rods for controversy. The prin-
ciple of common but differentiated responsibilities and respective capabilities
(CBDR-RC)—arguably the most well-known example of differential treatment—
ha, for instance, been one of the most frequently debated features of the United
Nations Framework Convention on Climate Change (UNFCCC). For some, it is the
ultimate expression of climate justice—an official acknowledgment of the vast
inequalities pervading global environmental politics (Soltau 2009). For others, Esso
is something altogether different: a dysfunctional relic that has seared a North–
South divide into the heart of the climate regime, constituting its “greatest weak-
ness” (Depledge and Yamin 2009, 443).
Curiously, despite the high level of controversy surrounding differential
treatment, research has been limited in an important way. There are, today,
many qualitative studies of differentiation within individual regimes. The liter-
ature on CBDR-RC is vast, and many have explored differentiation in specific
domini, such as in the ozone and climate regimes (Biermann 1997; Castro
and Kammerer 2021; Pauw et al. 2014; Pauwelyn 2013; Thompson 2020).
But relatively less work looks at these arrangements from a quantitative perspec-
tive, and key hypotheses have gone unexplored as a result. Within the field of
global environmental politics, Per esempio, quantitative researchers have evalu-
ated theories about numerous aspects of international treaties, including their
legal form, duration, escape clauses, institutional arrangements, and much more
beyond (Mitchell et al. 2020). Yet, important exceptions aside, differentiation
has not featured prominently.1 Our understanding of the drivers, dynamics,
and impacts of differentiation has therefore been constrained, and it is unclear
whether findings from qualitative studies and relevant formal models generalize
when we consider a large number of cases.
One reason why differentiation has not been investigated extensively in
quantitative research on environmental treaty making is because data on how
it manifests in agreements remain limited. At present, we have information on
numerous dimensions of environmental treaties. The International Environ-
mental Agreements Database (IEADB), in particular, has served as the starting
point for many studies that have carefully measured various aspects of institu-
tional design, such as those described earlier (Mitchell et al. 2020). These efforts
have made it possible to move beyond case studies and toward “large-N”
1. This is also true of the literature on treaty making beyond the environmental realm. Koremenos
(2016), for instance, has explored many features of international agreements, but differentia-
tion has not been a major object of study. While her work has examined “asymmetries of
controllo,” which is somewhat similar, since weighted voting rules do “differentiate” between
members, this is not the type of differentiation with which we are concerned. Only recently
has this begun to change as scholars like Ella (2020) have sought to correct this oversight.
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Deborah Barros Leal Farias and Charles Roger
(cid:129) 119
analyses of institutional variation. Accordingly, we have learned a great deal
about how treaties are made, how they evolve, and how they matter. Generally,
Anche se, these efforts have not extended to provisions for differentiation. So far,
the most significant has been that undertaken by Breitmeier et al. (2006). Yet,
their resource—the International Regimes Database (IRD)—only covers a small
sample of agreements across twenty-three regimes, and differentiation has not
featured extensively in published work that has built on the IRD. In definitiva,
without suitable measures, it has been challenging to study them using quanti-
tative tools.
In this Research Note, we describe one way of relieving this constraint, we
shed new light on historical patterns of differential treatment, and we show how
the data we collect can be used to evaluate a crucial but thus far untested con-
jecture about how these provisions matter. In the first section, we discuss our
data collection strategy, which relies on the IEADB and especially the 1,300-plus
multilateral environmental agreements (MEAs) it contains.2 Within this set, we
exploit use of the term developing countries, and equivalent language, to track
instances of differentiation and produce a list of agreements with these provi-
sions (see the online Appendix). The second part of the article then draws a
comprehensive picture of these agreements, offering several new insights. Noi
show, specifically, that they are older than commonly supposed, dating back
to the early 1960s, but that nearly 75 percent of the MEAs offering differential
treatment have appeared in the increasingly ambitious set of environmental
treaties that have been signed since the 1990s. They are also surprisingly infre-
quent, appearing in only 6 percent of agreements, but are particularly common
in larger ones that bring together more diverse groups of states. As such, Essi
appear to be used quite selectively.
Why does differentiation disproportionately appear in larger, newer, more
ambitious MEAs? We argue that differential treatment has played an important
role in these agreements. We illustrate how this is so in the final section by revi-
siting the debate on the depth–participation dilemma. The theoretical logic
behind the dilemma is intuitive, and it has been the focus of numerous studies.
È interessante notare, Anche se, empirical evidence that it exists has been largely missing.
We show—in line with the key expectation from the formal model advanced by
Gilligan (2004)—that the trade-off is conditioned by the scope for differentia-
tion in an agreement. Specifically, by extending a prior quantitative analysis by
Bernauer et al. (2013), we demonstrate that when there are no provisions for
differentiation, greater “depth” indeed reduces participation. Tuttavia, Quando
such provisions are present, it becomes possible to sustain high levels of both.
This powerfully illustrates the work that differentiation performs in these agree-
ments and how it interacts with other elements of institutional design, and it
2. As discussed later, we follow IEABD’s definition of an international environmental agreement
(IEA): “an intergovernmental document intended as legally binding with a primary stated pur-
pose of preventing or managing human impacts on natural resources.” MEAs are the subset of
IEAs with three or more parties.
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120 (cid:129) Differentiation in Environmental Treaty Making
indicates that further research exploring these dynamics would be rewarding.
Future studies on how states choose between alternative approaches to differen-
tiation, how differentiation evolves within regimes, and how this shapes state
behavior are likely to be particularly productive.
Measuring Differentiation for Developing Countries
Much has been written about differential treatment, particularly in the environ-
mental realm. Legal scholars like Rajamani (2006) have extensively investigated
the complex rules that divide environmental obligations asymmetrically across
stati (see also Alam et al. 2015; Honkonen 2009; Magraw 1990). Scholars in
international relations (IR) have explored the politics surrounding these provi-
sions too, focusing especially on a few particularly prominent cases. In global
environmental politics, Per esempio, the principle of CBDR-RC has been a
major focus of inquiry, especially within qualitative studies of the climate
and ozone regimes (Biermann 1997; Castro and Kammerer 2021; Ella 2017;
McGee and Steffek 2016; Prys-Hansen and Franz 2015; Thompson 2020).
Ma, in IR, relatively few have taken a quantitative approach that looks across
regimes to understand these provisions. While many scholars have explored dif-
ferent elements of treaty design and ratification using such tools (Koremenos
2016; Mitchell et al. 2020)—and though there are, certainly, some key excep-
zioni, such as Breitmeier et al. (2006) and Ella (2020)—differentiation has
largely remained on the sidelines. Correspondingly, important hypotheses,
such as Gilligan’s (2004) conjecture about how differentiation can “break”
the harsh logic of the depth–participation dilemma, have not been explored
systematically.
This omission is surprising given the controversy that has often sur-
rounded differential treatment. It is understandable, Tuttavia, in view of the
limited data that exist on this dimension of treaty design. Even basic quantita-
tive information about these provisions has often been difficult to come by. In
contrast with many other treaty provisions (Mitchell et al. 2020), we still only
have illustrative lists of treaties with differentiation, such as the seventeen prom-
inent examples compiled by Rajamani (2006, 119–121), and smaller samples
of these agreements within specific regimes, such as those in the IRD. One of the
key reasons for this, we argue, is because differentiation can take a variety of
forme. In practice, it can include, first, unequal burden sharing with respect to
central obligations, such as the quantitative targets under Kyoto; second, differ-
ences in their implementation, such as the extended schedules and varying
reporting requirements in the UNFCCC; and third, targeted financial or tech-
nical assistance to help specific groups of states comply with global rules
(Rajamani 2006). This variation in the way differentiation manifests in agree-
ments makes it challenging to track and compare these provisions.
That said, one overlooked feature of treaties with differentiation is that
they typically single out a distinct set of “developing” parties. Infatti, they often
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Deborah Barros Leal Farias and Charles Roger
(cid:129) 121
explicitly recognize “developing countries,” or employ similar or related terms,
to highlight their unique needs and priorities. This terminology is relatively
standardized, provides an explicit rationale for deviating from the principle of
sovereign equality, and is used to allocate unique rights and obligations to par-
ticular countries (French 2000; Magraw 1990; Rajamani 2006). While there are
treaties that have “implicit” norms affording some level of differential treat-
ment, or that may rely on other kinds of flexibility mechanisms (like treaty res-
ervations) as a substitute, agreements that clearly identify “developing country”
parties generally do so because they intend to give them special legal consider-
ation.3 The presence of such terms, Perciò, sends a strong signal that an agree-
ment includes provisions for differentiation of one kind or another.
Here, we leverage this feature to measure differential treatment in a more
systematic and efficient way than has been possible so far. To do so, we make
use of the IEADB, which is the most complete database of its kind (Mitchell
et al. 2020). In it, an environmental agreement is defined as “an intergovern-
mental document intended as legally binding with a primary stated purpose
of preventing or managing human impacts on natural resources.” This consti-
tutes a purposefully broad understanding of what is considered “environmen-
tal,” ensuring that agreements dealing with many issues are included.4 At the
same time, the IEADB is restricted to agreements that are binding under inter-
national public law and that operate differently from environmental “soft law”
(Boyle 2021). Così, nonbinding agreements, such as the 1972 Stockholm
Declaration on the Human Environment and the 1992 Rio Declaration on
Environment and Development—though important—are excluded.
Presently, the database includes approximately 4,000 treaties, most of
which are bilateral in nature. We focused on the 1,305 MEAs it contains—the
subset most relevant to this study. This means, in practice, agreements that have
three or more parties. Our analysis proceeded, first, by conducting an auto-
mated search to identify all the MEAs pairing the word “developing” with
“country/countries,” “state(S),” “member(S),” “parties(S),” or “partner(S).”5
Because some MEAs include special responsibilities for “developed countries”
or “industrialized states,” we filtered the documents for these terms too. IL
initial output was a smaller selection of 250 “candidates,” which contained at
3. Note, Tuttavia, that some of these may be less relevant to environmental treaties. Treaty reser-
vations can, to a degree, offer states the ability to “self-differentiate.” Yet Koremenos (2016,
163) has shown that the use of reservations is relatively low in environmental agreements. Questo
may be because efforts to govern environmental problems are likely to be jeopardized by free
riding, and policy makers have a strong incentive to write provisions for differentiation into the
text of an agreement when distributional issues are a concern. Rather than leaving this up to
individual states, exceptions are addressed explicitly.
4. Others who have made extensive use of the database have sometimes removed treaties, like the
Agreement Establishing the World Trade Organization, that seem to exceed these boundaries
(Morin et al. 2018). We opted to leave these in to maintain consistency with the IEADB’s cod-
ing. Ma, in practice, removing these makes no difference to the findings we present.
5. È interessante notare, while we also searched for other frequently used terms, such as “Third World,"
“underdeveloped countries,” and “Global South,” these were not found in any MEA.
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122 (cid:129) Differentiation in Environmental Treaty Making
least one use of these pairs of terms. But this only indicated when these words
were present. The approach did not tell us whether they were connected as a
single logical expression or whether the text indeed granted special treatment
to distinct groups of states. Così, an extra step was necessary: the manual exclu-
sion of “false positives.”
To do so, we examined each agreement where the relevant terms appeared
and assessed whether they were indeed used to grant special obligations, priv-
ileges, or considerations through a concrete injunction. Most cases that fell short
were instances where “developing” was used as a verb or in an organization’s
name. This process also revealed, Anche se, additional instances where the terms
were used in a purely descriptive way and did not obviously result in special
treatment. Examples included treaties that mentioned developing countries in
a preambular paragraph without a clear injunction to act. Possibly, such uses
signal cases of implicit differentiation that is not specified in a legal text
(Magraw 1990; Rajamani 2006). Tuttavia, we took a conservative approach
and excluded these agreements. Following these exclusions, the agreements
that remained were ones that clearly led to differentiation for developing
states—typically, by assigning different obligations, varying modalities for
implementation, or providing targeted assistance.
Did this approach identify all instances of differential treatment? No
doubt, the “universe” of cases is larger. We focused on agreements where differ-
entiation for developing states was made explicit in a legally binding text. Ma
differentiation can appear in soft law or may operate through “contextual
norms” that shape how provisions are later interpreted (Magraw 1990). Some
agreements may also use idiosyncratic terms. Tuttavia, there is some reason to
think it performs well overall. One way to judge the validity of our approach is
to compare our data set with the extant sources mentioned earlier. Looked at
Da questa parte, we find that our technique identifies the majority of agreements. In
total, 90 percent of those in Rajamani’s list show up in our data set, for instance,
E, notably, the cases our approach failed to identify (like the World Heritage
Convention) are ones where implicit differentiation is thought to occur
(Magraw 1990; Rajamani 2006). Our measure is also very strongly correlated
(φ = 0.82, P < 0.001) with the dichotomous measure of differentiation within
the forty-four treaties included in the IRD.6 Thus, while our approach may not
recover every instance of differentiation, we can be confident that it captures the
most explicit and prominent cases.
Patterns of Differentiation in Environmental Treaties
As noted already, basic quantitative information about the historical frequency of
these provisions and the types of agreements in which they appear has often been
6. For this calculation, we have only included agreements in the IRD that also appear in the
IEADB. Note that in cases where coding has “diverged,” we have not attempted to exclude or
include cases.
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Deborah Barros Leal Farias and Charles Roger
(cid:129) 123
Table 1
MEAs With and Without Differentiation
All MEAs
Original agreements
Protocols
Amendments
Total
1,305
511
228
566
With Differentiation
81
52
12
17
difficult to obtain. Before moving to the analysis, we therefore present some basic
descriptive statistics, demonstrating that differentiation has appeared in a unique
set of MEAs. Indeed, our first key finding is that very few agreements differentiate
between parties. Of the 1,305 MEAs we examined, only 81 have these sorts of
provisions (see Table 1). Of these, 52 are “original” agreements and 29 are
amendments or protocols. This is equivalent to 6 percent of all MEAs, 10 percent
of all original agreements, and 4 percent of all amendments/protocols. For many,
this may be somewhat surprising given the amount of attention these provisions
have attracted. As discussed, differentiation has long been a source of controversy.
But this controversy clearly centers on a narrow set of agreements—ones with a
particular suite of design characteristics that are particularly relevant to the
depth–participation dilemma, as we discuss later.
Second, we find that differentiation is somewhat older than earlier studies
have suggested. The literature on international environmental law often refers to
the 1972 Stockholm Declaration on the Human Environment as the first agree-
ment in which differentiation appears and the 1982 United Nations (UN) Con-
vention on the Law of the Sea as the first “proper” MEA with provisions for
differentiation (Pauw et al. 2014; Rajamani 2006). The ozone regime is also often
noted as being important for the principle of CBDR-RC, in particular (Pauw et al.
2014; Rajamani 2006; also see Biermann 1997). This has led many earlier
studies to associate the emergence of differentiation with broader calls for a
New International Economic Order within the UN system ( Williams and
Montes 2016, 115–116). No doubt, this was an important period, as we discuss.
We find, however, that the very first differentiated MEA—the 1960 Statute of the
Intergovernmental Oceanographic Commission (IOC)—predates these agree-
ments by more than a decade.
While the practice is therefore older than previously thought, our third find-
ing is that most of these agreements are more recent. Almost 200 MEAs were con-
cluded between the end of World War II and the signing of the IOC Statute, and
none of these had provisions for differentiation. Even in the period immediately
after, while the number increased, such provisions were deployed in only a few
treaties (see Figure 1). The 1970s–1980s were indeed important, since the num-
ber of MEAs differentiating between states began to pick up during this period.
But it was only in the 1990s—a period of particularly ambitious environmental
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124 (cid:129) Differentiation in Environmental Treaty Making
Figure 1
MEAs with Provisions for Differentiation, 1945–2020
treaty making—that they started to increase significantly. Between 1945 and
1989, only 5 percent all MEAs included these provisions. In the 1990s, 11 percent
(and 15% of original agreements) did. And, in total, 75 percent of all the MEAs
with provisions for differentiation have appeared since this time.
Differentiated agreements have, therefore, primarily appeared in so-called
new-generation MEAs—where “depth” may be proportionately greater. Yet,
within this set of MEAs, we also find that differentiation has primarily been uti-
lized in agreements with a specific membership profile. As shown in Figure 2,
many MEAs are small: 39 percent have been ratified by 10 or fewer states, 41
percent have between 10 and 100, and only 20 percent have more than 100
Figure 2
Number of State Ratifications, 2020
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Deborah Barros Leal Farias and Charles Roger
(cid:129) 125
(Mitchell et al. 2020). In contrast, we find that differentiated MEAs are larger: 44
percent have been ratified by more than 100 states, 45 percent are medium
sized, and only 11 percent have 10 or fewer ratifiers. Furthermore, while only
6 percent of all MEAs differentiate, as noted, these provisions appear in nearly
30 percent of those that include more than 100 ratifications. Thus, they not only
appear in more recent and arguably more ambitious agreements but are dispro-
portionately used in those that involve larger groups of states, where there may
be starker economic, environmental, and ideological differences between
parties. In agreements where there may be fewer such differences—for example,
smaller treaties between similarly positioned states within a single region—and
where levels of ambition are lower, they have been used relatively less.
Analysis: Revisiting the Depth–Participation Dilemma
The selective use of differential treatment suggests that it performs an important
function in environmental treaties. In what follows, we examine how this is
so—and demonstrate the value of our data—by analyzing how differentiation
reshapes the depth–participation dilemma. This is especially useful, as noted,
because our data allow us to evaluate an important but thus far untested conjec-
ture advanced by Gilligan (2004). The literature on the dilemma is interesting,
overall, because while the theoretical logic underlying the trade-off is intuitive,
there is virtually no empirical evidence showing that it exists. The basic idea,
partly grounded in work by Downs et al. (1996), is that when an agreement is
more demanding, participation should shrink, since more countries find it costly
to comply. If so, this suggests that large-scale cooperation is problematic. Agree-
ments with significant participation are likely to be those that ask little of
members, and deeper ones should only attract smaller groups. So far, though,
pessimism seems unwarranted, since many agreements appear to combine these
features fairly successfully (Kahler 1992). Slapin and Gray (2014) have even
found a positive relationship, suggesting that they often go together.
A key question has been why this is. One suggestion by Bernauer et al.
(2013) is that other design features can incentivize participation. By facilitating
compliance, by providing dispute settlement mechanisms, and by creating
secretariats that can help build capacity, they argue that compliance costs can
be offset, leading to more participation. Their cross-sectional study finds little
evidence of a trade-off and provides support for their claims. However, they
are not the first to have advanced such an argument. In 2004, Gilligan devel-
oped a formal model showing that the trade-off only holds when states set
policies at an identical level. When an agreement sets policies at different levels,
the relationship is attenuated. Theoretically, Gilligan’s argument is sound.
Furthermore, there is some qualitative work that supports his idea. Biermann
(1997) has shown, for instance, how important differentiation has been for
bridging the gap between developed and developing states in the ozone regime,
one of the most successful MEAs, and Grubb et al. (1999, 84) have explained
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126 (cid:129) Differentiation in Environmental Treaty Making
how moving away from a “flat-rate” commitment under Kyoto was essential for
keeping states on board while shifting away from a “lowest common denomi-
nator target.” Thus far, however, his model has not been systematically tested in
quantitative work on the depth–participation trade-off. Bernauer et al.’s (2013)
study cites Gilligan’s work, for instance, highlighting differentiation as an exam-
ple of the features they have in mind, but does not explore its impact explicitly.
Our data can be used to evaluate Gilligan’s idea—deepening our under-
standing of participation-inducing design features to which Bernauer et al. call
attention—since the kind of differentiation on which we focus constitutes a par-
ticularly powerful way of enabling variation in commitments. To do so, we
revisit Bernauer et al.’s (2013) analysis, which uses the IEADB and assesses
predictors of higher participation, measured via MEA ratifications. They look, spe-
cifically, at the set of MEAs that are “open,” with no restrictions on participation,
and where state diversity is likely to be a uniquely relevant consideration—
approximately 200 agreements. They then include separate indicator variables
for the three dimensions of “depth” on which they focus: quantitative targets,
monitoring arrangements, and enforcement mechanisms. Added to this are
measures of the participation-inducing features they identify: general provisions
for assistance, dispute settlement mechanisms, and the presence or absence of a
secretariat. Finally, they include controls for problem type, issue area, and so on.
To assess Gilligan’s (2004) model, we have modified Bernauer et al.’s
study somewhat. First, by adding together their three separate indicators of
depth, we created a single continuous measure, Depth. Agreements with all three
features establish “deep” commitments, those that have none are “shallow,” and
there is variation between these poles. This captures the idea of greater or lesser
depth, since agreements that combine quantitative targets, monitoring, and
enforcement are likely to be the most stringent; those that lack one or the other,
or all, will be less so. As Koremenos (2016) has shown, agreements with quan-
titative targets are much more likely to address problems characterized by free
riding, which, in turn, require strong monitoring and enforcement arrangements
to sustain cooperation. When all three are combined, therefore, cooperation is
likely to be especially meaningful, and adjustment costs may be correspond-
ingly high, all other things being equal. Second, we have added a dichotomous
variable that measures Differentiation. This indicates whether an MEA in their
data set is one we identified as offering differential treatment. Since Gilligan’s
(2004) model suggests that the depth–participation relationship is conditioned
by differentiation, we expect an interaction effect between these variables. When
differentiation is not present, deep commitments should be associated with
lower participation; when it is, high levels of both should be possible.
The results, presented in Table 2, confirm these expectations.7 Model 1
shows the bivariate relationship between Depth and the outcome, Ratification.
7. Replication materials for the statistical analysis are available at https://www.developingcountries
.info/projects-6, last accessed September 21, 2022.
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Table 2
Regression Results
Variable
Depth
Differentiation
Depth × Differentiation
General Assistance
Dispute Settlement
Secretariat
Global Public Good
Global and Domestic Good
Pollution
Species
Nuclear
Habitat
Age
Constant
Observations
(1)
(2)
(3)
(4)
−0.0988 (0.0817)
−0.200** (0.0925)
−0.204** (0.0923)
0.760*** (0.204)
0.147 (0.433)
0.0864 (0.431)
0.349* (0.200)
0.453** (0.196)
0.239 (0.226)
0.509*** (0.142)
−0.330 (0.207)
−0.578*** (0.203)
−0.497 (0.400)
−0.185 (0.192)
−0.531*** (0.199)
−0.0395 (0.241)
−0.412** (0.193)
0.0166*** (0.00600)
3.615*** (0.148)
3.290*** (0.0922)
3.613*** (0.157)
3.842*** (0.328)
213
213
213
211
Robust standard errors in parentheses.
*p < 0.1.
**p < 0.05.
***p < 0.01.
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128 (cid:129) Differentiation in Environmental Treaty Making
Estimated by negative binomial regression, as in Bernauer et al.’s study, it
demonstrates that while these are negatively related, the coefficient is not
significant—a null finding exemplifying the puzzle in this literature. Model 2
shows the relationship between Ratification and Differentiation. The coefficient,
in this case, is positive and significant. This makes sense given that differentiated
agreements tend to be larger. Model 3 includes both component variables plus
the interaction term. Here, we find that Depth is negatively related with Ratifica-
tion and statistically significant when there is no differentiation (i.e., Differenti-
ation = 0). Differentiation is positive but no longer significant, indicating that
when an agreement is shallow (i.e., Depth = 0), there is little evidence that it
affects participation. Crucially, though, the interaction term is significant and
positively signed. This indicates that Depth and Ratification are increasing when
agreements differentiate between parties. Finally, Model 4 demonstrates that
these results hold after introducing additional variables from Bernauer et al.’s
(2013) study, including measures of the participation-inducing features they
identify and various controls. Most of these perform as they do in their study,
showing that the features to which they call attention continue to be important.
To make these results more concrete, in Figure 3 we present marginal
effects estimates and 95 percent confidence intervals derived from model 4
for a set of key values. On the left side, we show how treaty ratification is pre-
dicted to vary when differentiation is high and low and when commitments are
shallow. As before, this reveals that differentiation makes little difference to the
outcome. Ratifications are marginally higher when a treaty offers differential
treatment, but both are predicted to have a relatively large number of ratifica-
tions, aligning with the idea that when agreements are not very demanding, they
can induce high participation. The right side shows the effect of differentiation
when commitments are “deep,” that is, Depth = 3. In this case, the expected
Figure 3
Marginal Effects Estimates
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Deborah Barros Leal Farias and Charles Roger
(cid:129) 129
number of ratifications drops by 50 percent when Differentiation = 0. Again, this
confirms the expectation from Gilligan’s (2004) model that depth and partici-
pation are negatively related when state policies are set at similar levels. Ratifi-
cations then rise when commitments are deep and an agreement offers
differentiation. Substantively, the change is quite large—more than double the
ratifications expected when commitments are shallow.
These results have important implications. Most obviously, they show that
differentiation has a powerful effect on state behavior, significantly affecting the
prospects for deep cooperation between larger, more diverse groups. From a
policy perspective, this is a valuable insight that helps to explain why policy
makers have heavily relied on these provisions throughout a particularly ambi-
tious period of environmental treaty making. But additionally, these results help
reconcile two puzzles in the literature on these dynamics. First, if the depth–
participation dilemma is indeed conditioned by differentiation, as we find, this
may explain why earlier studies have not discovered evidence of it. If the trade-
off is expected to appear only in specific circumstances, which have not been
accounted for statistically, it should be relatively unsurprising that earlier studies
do not recover the corresponding relationship. Second, this may help to explain
why some, like Kahler (1992) and Slapin and Gray (2014), have found the
opposite: that depth and participation sometimes go together. Generally, this
has been taken as evidence against the trade-off. But this is not so puzzling—
or damning—once we recognize the work differentiation may be doing. Where
present, it can short-circuit the depth–participation dilemma, as Gilligan (2004)
has suggested, making it possible to have high levels of both.
Conclusions
Our aim in this Research Note has been to shed new light on differentiation in
international treaty making—how often it occurs, when it does, and how it
matters. This design feature has been of considerable interest to scholars but
has been challenging to study due to data constraints. We have proposed one
way of relieving these constraints, presented evidence of the frequency of these
provisions, and demonstrated their impact on state behavior. Our results show
that differentiation is used infrequently, but strategically, appearing in newer
treaties involving larger groups of states. Overall, it appears to play an important
role by helping countries to reconcile their differences and achieve deeper coop-
eration than would otherwise be possible. From a methodological perspective,
we also demonstrate how important it is to account for these provisions in our
analyses and how doing so can reconcile conflicting conclusions reached by
earlier researchers.
For these reasons, it will be important to devote further attention to dif-
ferential treatment. Here, we have illustrated how differentiation reshapes the
depth–participation dilemma and confirmed a key untested conjecture, but
there are grounds for thinking that differentiation has complex relationships
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130 (cid:129) Differentiation in Environmental Treaty Making
with other aspects of institutional design and state behavior. On the institu-
tional design front, differentiation may condition choices about other flexibility
mechanisms, the legal form of an agreement, and how regimes evolve over time.
In terms of state behavior, where differentiation is not available, states may
introduce their own forms of flexibility, such as treaty reservations or contextual
norms that shape how agreements are implemented. Future researchers may
also find it useful to subset our data, exploring how states choose between var-
ious forms of differential treatment and how these matter in different contexts.
In short, we believe there is a rich set of questions about these provisions that
requires careful investigation and that the answers to them may hold important
insights for policy makers seeking to resolve environmental challenges fairly and
effectively.
Deborah Barros Leal Farias is a senior lecturer at UNSW-Sydney. One of her
main research interests is the intersection of power, classification, and country
identities, particularly attentive to the interests of developing countries and to
the role of international governmental organizations. She is the creator of the
Developing Countries Database project (https://www.developingcountries.info)
and author of Aid and Technical Cooperation as a Foreign Policy Tool for Emerging
Donors: The Case of Brazil (Routledge, 2018).
Charles Roger is an assistant professor and Beatriu de Pinós Research Fellow at
the Institut Barcelona d’Estudis Interncionals (IBEI) and a visiting fellow at the
Robert Schuman Centre for Advanced Studies of the European University Insti-
tute (EUI). He is the author of The Origins of Informality: Why the Legal Founda-
tions of Global Governance Are Shifting, and Why It Matters (Oxford University
Press, 2020) and a coauthor (with Harriet Bulkeley et al.) of Transnational Cli-
mate Change Governance (Cambridge University Press, 2014).
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