Assortative Matching of Exporters and Importers*
Yoichi Sugita†
Kensuke Teshima‡
Enrique Seira§
Luglio 2021
Astratto
This paper studies how exporting and importing firms match based on their ca-
pability by investigating the change in such exporter–importer matching during trade
liberalization. During the recent liberalization on the Mexico-US textile/apparel trade,
exporters and importers often switch their main partners as well as change trade vol-
umes. We develop a many-to-many matching model of exporters and importers where
partner switching is the principal margin of adjustment, featuring Beckerian posi-
tive assortative matching by capability. Trade liberalization achieves efficient global
buyer–supplier matching and improves consumer welfare by inducing systematic part-
ner switching. The data confirm the predicted partner switching patterns.
JEL Classification: F1; Keywords: Firm heterogeneity, assortative matching,
two-sided heterogeneity, trade liberalization
*We are grateful to comments from three anonymous referees and the editor Amit Khandelwal, particolarmente
their encouragement for many-to-many matching extensions. We thank Andrew Bernard, Bernardo Blum,
Kerem Cosar, Don Davis, Swati Dhingra, Lukasz Drozd, Michael Gechter, Julia Cajal Grossi, Meixin Guo,
Daniel Halvarsson, Keith Head, Wen-Tai Hsu, Mathias Iwanowsky, Hiroyuki Kasahara, Ben Li, Alberto
Ortiz, Nina Pavcnik, James Rauch, Bob Rijkers, Esteban Rossi-Hansberg, Peter Schott, Yuta Suzuki, Heiwai
Tang, Yong Tang, Catherine Thomas, Kosuke Uetake, Yasutora Watanabe, Yuta Watabe, David Weinstein,
Shintaro Yamaguchi, Makoto Yano and participants at seminars and conferences for their comments. Noi
thank Secretaria de Economia of Mexico and the Banco de Mexico for help with the data. Financial supports
from the Private Enterprise Development in Low-Income Countries (PEDL), the Wallander Foundation, IL
Asociacion Mexicana de Cultura, and JSPS KAKENHI (Grant Numbers 22243023, 26220503, 15H05392,
17H00986, 18K19955 and 19H01477) are gratefully acknowledged. This research benefits from the IDE-
JETRO project and the RIETI project. Francisco Carrera, Diego de la Fuente, Zheng Han, Carlos Segura,
Yuri Sugiyama, Yuta Suzuki, Jumpei Takubo, Makoto Tanaka, and Stephanie Zonszein provided excellent
research assistance.
†Graduate School of Economics, Hitotsubashi University. 2-1 Naka Kunitachi, Tokyo 186-8601, Japan.
(E-mail: yoichi.sugita@r.hit-u.ac.jp)
‡Institute of Economic Research, Hitotsubashi University. 2-1 Naka Kunitachi, Tokyo 186-8601, Japan.
(E-mail: kensuke-teshima@ier.hit-u.ac.jp)
§ITAM. Av. Santa Teresa # 930, Mexico, D. F. 10700 (E-mail: enrique.seira@itam.mx)
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1 introduzione
International trade mostly takes the form of firm-to-firm transactions in which firms seek and com-
pete for capable buyers and suppliers globally. A case example is Boeing’s 787 Dreamliner team
that comprises the most capable suppliers from all over the world. Trade research in the last two
decades has revealed the huge heterogeneity in the capability of exporters and importers (per esempio., their
productivity and product quality). Così, the way heterogeneous exporters and importers match
along the supply chains may determine the aggregate capability of the industry and the welfare.
This paper examines how exporters and importers match based on their capability by investi-
gating the change in such exporter–importer matching during trade liberalization. From Mexico’s
customs administrative records, we construct a matched exporter–importer dataset for Mexican
textile/apparel exports to the United States from 2004 A 2007. Mexico–US textile/apparel trade
is particularly suitable for our purpose. Primo, since Mexico and the United States are large trad-
ing partners with each other, trade between them includes numerous heterogeneous exporters and
importers.1 Second, Mexico–US textile/apparel trade experienced large-scale liberalization. In
2005, the United States removed quotas on textile/apparel imports at the end of the Multi-Fibre
Arrangement (MFA). Since Mexican products already had quota-free access to the US market
under the North American Free Trade Agreement (NAFTA), the MFA’s end effectively removed
protection for Mexican products in the US market and forced them to compete with imports from
third countries, principally China. The liberalization varied across products substantially and was
arguably exogenous because the liberalization schedule was decided at the GATT Uruguay Round
(1986–94) when China’s export growth were not expected.
The MFA’s end substantially changed the partnerships between Mexican exporters and US im-
porters. Mexican exports to the United States decreased by the extensive margin (stopping exports)
1In 2004, the United States was the largest textile and apparel market for Mexico, while Mexico was the
second largest source for the United States. Infatti, 91.9% of Mexican exports are shipped to the United
States and 9.5% of US imports are from Mexico.
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and intensive margin (reducing export values). The intensive margin adjustment involved substan-
tial partner switching, often including the exporter’s largest main partners. Main partner switching
accounted for more than 50% of the intensive margin and caused a more than 230% excess re-
allocation of exports across US buyers beyond the intensive margin. As we explain in Section
2, this prevalence of main partner switching in trade liberalization was at odds with anonymous
market models (per esempio., neoclassical models, oligopoly models), love-of-variety models (the Krug-
man–Melitz model), and some recent exporter–importer matching models (per esempio., Bernard, Moxnes,
and Ulltveit-Moe, 2018) that combine the love-of-variety model and fixed costs of matching.
Motivated by this new fact, we develop a many-to-many matching model of exporters and
importers in an intermediate good market in which partner switching is the principal margin of
adjustment. The model combines Sattinger’s (1979) frictionless assignment model of a contin-
uum of agents, Melitz’s (2003) standard heterogeneous firm trade model, and Bernard, Redding,
and Schott’s (2011) multi-product firm trade model. The model consists of final producers (io sono-
porters) in the United States and suppliers (exporters) in Mexico and China. Final producers pro-
duce multiple products, while suppliers own multiple production lines. A final producer’s variety-
level capability depends on its firm-level capability and idiosyncratic capability, while a supplier’s
production-line-level capability depends on its firm-level capability and idiosyncratic capability. UN
final variety matches a production line one-to-one, resulting in the many-to-many matching of final
producers and suppliers. The Beckerian PAM of varieties and production lines arises as a stable
equilibrium when a variety’s capability and production’s capability are complements.
The model predicts that the MFA’s end induced systematic partner switching that led to effi-
cient buyer–supplier matching and improved consumer welfare. As empirically documented by
Khandelwal, Schott, and Wei (2013), at the MFA’s end, Chinese suppliers at various capability
levels entered the US market. The entry of Chinese suppliers lowered the capability ranking of
each Mexican supplier in the market. Therefore, to achieve PAM, Mexican exporters switched
to US importers with lower capability, while US importers switched to Mexican exporters with
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higher capability. We call these types of partner switching “partner downgrading” and “partner
upgrading,” respectively. Allowing capable Chinese suppliers to match with capable US final pro-
ducers, this rematching achieved PAM in the global market, which improved aggregate capability
and consumer welfare. By contrast, in an anonymous market in which matching is independent of
capability, rematching should not occur in a systematic way or result in an efficiency gain.
We take the model’s predictions on partner switching to data. Guided by the theory, we estimate
the rankings of firm-level capability of Mexican exporters and US importers by the rankings of
their 2004 pre-liberalization product trade with their main partners. We then compare the partner
switching patterns between liberalized products (the treatment group) and other textile/apparel
prodotti (the control group) within Harmonized System (HS) two-digit industries. We find the
partner switching patterns to be consistent with PAM. Primo, US importers upgrade their Mexican
partners more often in the treatment group than in the control group. Allo stesso tempo, Mexican
exporters downgrade their US partners more often in the treatment group than in the control group.
Secondo, among firms that switch their main partners, the capability rankings of new partners are
positively correlated with those of old partners. Together, these findings provide strong support for
PAM and reject independent random matching. Inoltre, we confirm the model’s predictions
on firm exit and the number of partners. Primo, the capability cutoff for Mexican exporters increases.
Secondo, US importers and Mexican exporters decrease their number of partners.
To the best of our knowledge, detecting Beckerian PAM by capability in this way is a novel
approach to addressing the endogeneity problem in the conventional approach. When matching
matters for a firm’s performance, most firm characteristics observable in typical production and
customs data (per esempio., inputs, outputs, and productivity measures) may reflect partners’ unobserved
capability as well as the firm’s own capability. Therefore, the simple correlation of those charac-
teristics across matches may suffer from endogeneity.2 Instead, our approach utilizes the MFA’s
end as an exogenous negative shock on the capability ranking of Mexican exporters.
2For instance, Oberfield (2018) showed a buyer’s employment is positively correlated with a seller’s
employment in a model in which buyers match sellers randomly and independently of capability.
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As matched exporter-importer data become available to researchers, the last decade saw the
burgeoning literature on buyer-supplier relationships in international trade.3 Our paper contributes
to a strand of this literature studying exporter-importer matching. Rauch (1996), Casella and Rauch
(2002), and Rauch and Trindade (2003) pioneered the theoretical literature by using the assignment
model of symmetric firms, while our model features firm heterogeneity in capability as in Melitz
(2003). Antras, Garicano, and Rossi-Hansberg (2006) analyzed offshoring as the PAM of man-
agers and workers across countries. The assignment model captures two distinctive features in
exporter-importer relationships. Primo, trading with high capability firms improves a firm’s perfor-
mance, but the opportunity to trade with them is scarce and something that firms compete for. Questo
view echoes with recent evidence that trading with high capability foreign firms improves local
firm’s performance through various channels.4 Second, buyer–supplier matching is an allocation
of scarce trading opportunities. Così, trade liberalization induces partner switching to achieve a
globally efficient matching. We provide the first evidence for this matching mechanism.
Bernard et al. (2018) recently developed another approach combining match-level fixed costs
and the love-of-variety (CES) production function.5 A buyer and a supplier are matched when the
match surplus exceeds the match-level fixed costs. As the match surplus monotonically increases
in the buyer’s capability and the supplier’s, all the matches are realized except those between low
capability firms.6 Thus, the model can predict the negative degree assortativity reported by Blum,
Claro, and Horstmann (2010), Bernard et al. (2018), and others that a buyer’s number of partners
3Domestic buyer-supplier matched data has recently become available for research on domestic produc-
tion networks(e.g. Bernard, Moxnes, and Saito, 2019; Dhyne, Kikkawa, Mogstad, and Tintelnot, 2021).
4See e.g., De Loecker (2007) and Atkin, Khandelwal, and Osman (2017) for learning technologies;
Macchiavello (2010) and Macchiavello and Morjaria (2015) for reputation building; Tanaka (2020) for
improving management; and Verhoogen (2008) for quality upgrading. Trading with foreign multinational
firms is also found to improve firm’s performance (per esempio., Javorcik, 2004).
5Bernard, Dhyne, Magerman, Manova, and Moxnes (2021) and Lim (2018) introduced idiosyncratic
match-level fixed costs in the model of Bernard et al. (2018) and analyzed the formulation of domestic
production networks. Carballo, Ottaviano, and Volpe Martincus (2018) applied the ideal variety approach
instead of using the love-of-variety model, which incorporates the interaction between the buyer’s taste for
ideal varieties and the seller’s productivity.
6In the assignment model, by contrast, the match surplus is a non-monotonic function. For a given firm,
the match surplus is maximized at the capability of its equilibrium partner as we show in Section 3.1 (2).
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is negatively correlated with the average number of firms to which the buyer’s partners sell.
Our finding of PAM can be compatible with negative degree assortativity both theoretically
and empirically. In Appendix D, we present a two-tier model of exporter–importer matching that
unifies Bernard et al.’s (2018) model and ours to predict negative degree assortativity for the firm-
level matching and PAM for the product-level matching. In the model, a buyer (per esempio., a car maker)
has a love-of-variety production function with respect to intermediate goods and decides whether
to make or buy each intermediate good (per esempio., tires, seats), considering the match surplus and match-
level fixed costs, as in Bernard et al. (2018). For each intermediate good (per esempio., a set of four tires), UN
buyer matches a supplier following PAM as in our model. Our data confirm the model’s prediction
by finding that negative degree assortativity holds when a match is defined at the firm level, Ma
becomes weaker and statistically insignificant when a match is defined at the product level.
Another important strand of the literature studies the dynamics of an exporter’s and importer’s
partner choice in a steady-state environment. Macchiavello (2010) introduced reputation build-
ing in an assignment model to explain an exporter’s partner upgrading over time. Eaton, Eslava,
Jinkins, Krizan, and Tybout (2014) and Eaton, Jinkins, Tybout, and Xu (2015) developed models
incorporating search and learning frictions in partner acquisitions.7 Eaton, Kortum, and Kramartz
(2016) modeled random meeting and competition among multiple buyers and suppliers. Monarch
(2021) estimated partner switching costs in a dynamic discrete choice model. Ehi (2020) docu-
mented the dependence of exchange rate pass-through on the age of trade relationships.
Benguria (2021) and Dragusanu (2014) documented positive correlations between the size and
productivity measures of exporters and importers in France–Colombia trade and India–US trade,
rispettivamente. Our model featuring Beckerian PAM also predicts these findings. Benguria (2021)
and Dragusanu (2014) developed search effort models of the Stigler (1961) type to explain their
findings by a different mechanism: a high productivity exporter spends greater search efforts find-
ing a high productivity importer. Their models, Tuttavia, do not explain Mexican exporters’ partner
7Lu, Mariscal, and Mejia (2017) analyzed importer’s switching intermediates in a search/learning model.
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downgrading at the MFA’s end. In their models, search costs are sunk and importers are willing to
trade with all exporters. Così, Mexican exporters should continue to trade with pre-liberalization
US partners instead of downgrading partners by paying additional search costs.
Another related literature investigates non-anonymous contracts in given exporter-importer re-
lationships, using matched exporter-importer data. Macchiavello and Morjaria (2015) examined
the surplus of long-term relationships relative to anonymous spot trade. Cajal-Grossi, Macchi-
avello, and Noguera (2020) found greater markups in long-term relational trade than spot trade.
Bernard and Dhingra (2019) studied firm’s relationship investment to avoid inefficiency in spot
trade. Ignatenko (2019) reports exporter’s price discriminations across importers. Our paper com-
plements this literature by showing exporters match importers in an non-anonymous way, pure.
The rest of this paper is organized as follows. Sezione 2 explains our data and documents new
facts on partner switching during liberalization. Sezione 3 presents our model and derives predic-
zioni. Sezione 4 describes our empirical strategy. Sezione 5 presents the main results and robustness
controlli. Sezione 6 provides concluding remarks. The Online Appendix provides the calculations,
proofs, data construction, extended models, robustness checks, and additional analyses rejecting
alternative explanations of our results.
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2 Mexico–US Textile/Apparel Trade
2.1 The End of the MFA
The MFA and its successor, the Agreement on Textiles and Clothing, are agreements about the
quotas on textile/apparel imports among GATT/WTO countries. At the GATT Uruguay Round
(1986–94), the United States (together with Canada, the European Union, and Norway) promised
to abolish the quotas in four steps (In 1995, 1998, 2002, E 2005). The MFA’s end in 2005 era
the largest liberalization in which liberalized products constituted 49% of imports in 1990.
Three facts (taken from previous studies) about the consequences resulting from the MFA’s end
6
Review of Economics and Statistics Just Accepted MS. https://doi.org/10.1162/rest_a_01114 © 2021 by the President and Fellows of Harvard College and the Massachusetts Institute of Technology. Published under a Creative Commons Attribution 4.0 Internazionale (CC BY 4.0) licenza.
motivate our analysis.
Fact 1: Surge in Chinese Exports to the United States According to Brambilla, Khandelwal,
and Schott (2010), US imports from China disproportionally increased by 271% In 2005, while
imports from most other countries decreased. Using Brambilla et al.’s (2010) US import quota
dati, we classify each HS six-digit textile/apparel product into two groups (see Appendix B.5 for
details): the treatment group of products in which Chinese exports subject to the binding 2004 US
import quota, and the control group of other textile/apparel products. We regress the HS six-digit
product-year-level exports of China and Mexico on the annual year dummies with product fixed
effects separately for the treatment group and control group. Figura 1 shows the coefficients of
the annual year dummies with triangles for the treatment group and circles for the control group,
separately for Chinese exports and Mexican exports. The difference in the coefficients between
the two groups expresses the impacts of the MFA’s end on Chinese and Mexican exports after
controlling for product-specific effects. In the left panel for Chinese exports, while the coefficients
before 2005 are stable and virtually identical between the two groups, after the 2005 quota removal,
the coefficient for the treatment group increases much faster than that for the control group.8
<
Fact 2: Mexican Exports Faced Competition from China By 2003, Mexico already had tariff-
and quota-free access to the US market through NAFTA. With the MFA’s end, Mexico lost its
advantage over third-country exporters and faced increased competition from Chinese exporters in
the US market, as the right panel of Figure 1 shows.9 While the two groups were stable and almost
8After this substantial surge in import growth, the United States and China had agreed to impose new
quotas until 2008, but imports from China never returned to their pre-2005 levels because (1) the new quota
system covered fewer product categories than the old system (Dayaratna-Banda and Whalley, 2007) E (2)
the new quotas were substantially greater than the MFA levels (Vedi la tabella 2 in Brambilla et al., 2010).
9In theory, Mexican firms can export products to the US that are produced from materials imported
from China; Tuttavia, the number of such cases is negligible because of NAFTA’s restrictive rules of origin,
which requires “yarn forward” (US CBP, 2014). The yarn must be made in Mexico to be qualified as NAFTA
7
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Review of Economics and Statistics Just Accepted MS. https://doi.org/10.1162/rest_a_01114 © 2021 by the President and Fellows of Harvard College and the Massachusetts Institute of Technology. Published under a Creative Commons Attribution 4.0 Internazionale (CC BY 4.0) licenza.
identical before 2005, the exports in the treatment group significantly declined thereafter.
Fact 3: Exports by New Chinese Entrants with Various Capability Levels From Chinese
customs transaction data, Khandelwal et al. (2013) decomposed the increases in Chinese exports
to the United States in liberalized products after the removal of the quota into the intensive and
extensive margins. Increases in Chinese exports were mostly driven by the entry of new exporters
that had not previously exported products. These new exporters have different capability levels to
those of incumbent exporters, with many more capable than incumbents.10
2.2 Partner Switching after the MFA’s End
Data From Mexico’s customs administrative records, we construct a matched exporter–importer
dataset from June 2004 to December 2011 for Mexican textile/apparel exports (covering HS50 to
HS63) to the United States. For each match of a Mexican exporter and a US importer, the dataset
contains the following information: exporter ID, importer ID, HS six-digit product code, annual
shipment value (USD), quantity and unit, an indicator of a duty-free processing reexport program
(Maquiladora/IMMEX), and other information.
We assign the exporter ID and importer ID throughout the dataset. The exporter ID is the
tax number unique to each firm in Mexico. Assigning importer IDs to US firms is challenging.
Although the customs records report the name, address, and employment identification number
(EIN) of the US importer for each transaction, none of these can uniquely identify a firm because
it can use multiple names or change names, own multiple plants/establishments, or change tax
numbers. Inoltre, a firm’s name and address may be written in multiple ways and suffer
from typographical errors. Therefore, simply counting combinations of names, addresses, E
prodotti; Perciò, only fibers can be imported from China. Tuttavia, Mexico’s fiber imports from China
È 7 million USD in 2004 and accounts for only 0.08% of Mexico’s textile/apparel exports to the US.
10Khandelwal et al. (2013) reported that incumbent exporters are mainly state-owned firms, whereas new
exporters include private and foreign firms, which are typically more productive. Inoltre, the distribution
of unit prices set by new entrants has a lower mean but greater support than that by incumbent exporters.
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EIN would wrongly assign more than one ID to one US importer.
We therefore assign the importer ID by applying a series of record linkage techniques.11 First,
we prepare a list of name variations such as fictitious names, previous names, and name abbrevia-
zioni, a list of addresses of company branches/subsidiaries, and a list of EIN from Orbis by Bureau
van Dijk, which covers 20 million company branches, subsidiaries, and headquarters in the United
States. Secondo, the address format is standardized using software certified by the US Postal Office.
Third, we match the lists from Orbis to each of the linking variables (name, address, EIN) in the
customs data by fuzzy matching. Two types of errors can occur in fuzzy matching: “false match-
ing” (matching records that should not be matched) and “false unmatching” (not matching records
that should be matched). The criteria for fuzzy matching are chosen to minimize false unmatching
because false matching is easier to identify by manual checks. Fourth, binary matched records
are aggregated into clusters so that each record matches another record in that cluster. Then, we
manually check each cluster and remove falsely matched records. A resulting cluster represents a
firm and receives an importer ID. Appendix B explains the data construction process in detail.
Data cleansing drops some observations. Primo, since the dataset only covers observations from
June to December in 2004, we drop the observations from January to May in other years to make
the information in each year comparable. We obtain similar results when January–May observa-
tions are included. Secondo, while importer information is reported for most normal trade trans-
actions, it is sometimes missing for processing trade transactions under the Maquiladora/IMMEX
program in which exporters do not have to report an importer for each shipment.12 We drop ex-
porters that do not report the importer information for most transactions. To address the potential
selection issues caused by this action, we distinguish normal trade and processing trade in the
analyses below and conduct weighted regressions in Appendix B.4.
11An excellent reference for record linkage is Herzog, Scheuren, and Winkler (2007). Inoltre, we
benefitted from the lecture slides on “Record Linkage” by John Abowd and Lars Vilhuber.
12The Maquiladoras program started in 1986 and the IMMEX program replaced it in 2006. Under these
programs, firms in Mexico can import the materials and equipment to be used for exports duty free. Ex-
porters must register the importer’s information in advance but need not report it for each shipment.
9
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Tavolo 1 reports the summary statistics for the product-level and firm-level matching. A product-
level match occurs if an importer and an exporter trade in a particular product, while a firm-level
match occurs if an importer and an exporter trade in at least one product. Columns (UN) E (B) In
Tavolo 1 report the mean and median of the product-level matching.13 The first four rows show that
11–15 exporters and 15–20 importers exist in an average product market, but the majority of firms
trade with only one partner.14 Rows (5) E (6) show that even for firms that trade with multiple
partners, more than 70% of their trade occurs with their single main partners.15
<< Table 1 is here.>>
Excess Partner Switching after the MFA’s end Our new finding is that exporters and importers
actively switch partners during liberalization. Panel A in Table 2 reports the changes in Mexican
textile/apparel exports to the United States between 2004 E 2007 by incumbent exporters in 2004
separately for liberalized products (quota-bound) and other products (quota-free). The changes in
total exports in Column (1) are decomposed into the extensive margin in Column (2) by exiters
that stopped exporting by 2007 and intensive margin in Column (3) by continuing exporters in
2007.16 The intensive margin in Column (3) is further decomposed into three margins of partner
i cambiamenti: Partner Staying in Column (4) expresses the changes in exports to continuing buyers that
import from the exporter both in 2004 E 2007, Partner Adding in Column (5) expresses those
to new buyers in 2007 that did not import from the exporter in 2004, and Partner Dropping in
Column (6) expresses those to dropped partners that imported from the exporter in 2004 but not
13Tavolo 1 removes products with only one exporter or one importer, which accounts for 3% of trade.
Including them decreases the numbers in Columns (1) E (2), but barely changes those in the other columns.
14Appendix E.1 presents versions of Table 1 for 2005 E 2006 and for the regression samples that exclude
new exporters and new importers after 2005 that might have started with only one partner. The statistics on
the numbers of partners in Columns (3)–(6) remain close to those in Table 1.
15The large shares of trade with main partners in Table 1 are not driven by small firms that affect total
trade to an only small extent. In an earlier version of this paper, we reported that main-to-main matches,
where the exporter is the importer’s main partner for the product and the importer is the exporter’s main
partner, account for around 80% of total trade.
16In Appendix E.2, the extensive margin is decomposed into dropping products and leaving the US.
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In 2007. The parentheses in Columns (5) E (6) report the share of export changes by Partner
Switchers that simultaneously add and drop partners. These high shares imply that most partner
changes are in fact partner switching. Column (7) reports the excess reallocation of partners, cioè.,
|(5)| + |(6)| − |(5) + (6)|.
As Table 1 suggests, the switching of main partners plays a major role in the adjustment.
In Panel C in Table 2, the intensive margin in Column (1), which is Column (3) in Panel A, È
decomposed according to main partner’s involvement: export changes not involving main partners
in Column (2), exports to continuing main partners in 2004 E 2007 in Column (3), those to new
main buyers in 2007 that were not main buyers in 2004 in Column (4), and those to dropped main
buyers that were main buyers in 2004 but not in 2007 in Column (5). Column (6) reports the excess
reallocation associated with main partners, cioè., |(4)| + |(5)| − |(4) + (5)|.
<