Source
Source Contact person/organisation Contact person/organisation Data source(s) used Data source(s) usedSpecific terms and conditions apply to the use of these data: http://comtrade.un.org/db/help/LicenseAgreement.aspx
Data Characteristics Data Characteristics Unit of measure used Unit of measure used
Values are expressed in current USD. Users of OECD's International Trade Statistics databases should note that since February 2002, the national exchange rates for the Euro area countries have been converted into euros.
The option chosen by OECD is to convert exchange rates for periods prior to entry into European Monetary Union (EMU), i.e. prior to 1999 for all members apart from Greece, which acceded in 2001, from the former national currency exchange rate using the appropriate irrevocable exchange rate. Such a conversion facilitates comparisons over time within a country and also preserves the historical evolution (i.e. growth rates). However, pre-EMU euro rates are notional units and are not always suitable to form area aggregates or for cross country comparisons. For further details, see The Statistics Brief Number 2, February 2002.
Quantity units are: Area in square metres, Electrical energy in thousands of kilowatt-hours, Length in meters Longueur en mètres, Number of items, Number of pairs, Volume in liters, Weight in kilograms, Thousands of items, Number of packages, Dozen of items, Volume in cubic meters, Weight in carats.
Partner country: 280 individual areas are presented in ISO codes or in long label. Economic and geographic country groups are also presented. The geonomenclature is available online.
Flow: Imports, Exports, Re-imports and Re-exports.
Time: From 1961 depending on countries and classifications.
Notes that can be attached to data are: Estimated Value, Includes not available Value for products at lower level, Includes not available Value for detailed partners, Estimated net Weight, Estimated Quantity, Includes not available Quantity for products at lower level, Includes not available Quantity for detailed partners.
Population & Scope Population & Scope Statistical population Statistical populationThe OECDInternational Trade by Commodity Statistics database contains values and quantities of exports and imports by partner countries and by commodity or industry. Commodities are available at the most detailed level of the SITC (Revision 2 and 3) and the Harmonised System (HS 1988, HS 1996, HS 2002 and HS 2007).
The database dimensions are: reporter country, partner country, commodity, year, flow and value and quantity.
Thejoint OECD-UN Trade Data Collection and Processing System
The OECD and the United Nation Statistics Division (UNSD) have been working together during the past years to agree on the best statistical treatments of all aspects relating to international trade data and to align their respective data processing practices. Additional information on methodological changes is available in the online document The new and Operational UNSD-OECD Joint Trade Data Collection and Processing System, Methodological Issues.
Both organisations have identical data since 2005 and are also progressively aligning their historical data. The result is an improvement of data quality and data consistency.
Geographic coverage Geographic coverage The OECD Merchandise Trade Statistics Geonomenclature presents the components of the main economic and geographic zones as well as the detailed statistical territories. All detailed components are also available in Excel format.
Reporting countries:
Belgium-Luxembourg Economic Union: Since 1999, Belgium and Luxembourg henceforth publish separate foreign trade results. Belgium-Luxembourg Economic Union statistics are available from 1961 to 1992. Belgium data are available since 1993, while for Luxembourg, which can not provide historical data, data are available since 1999.
Belgium's statistics and Luxembourg's statistics are elaborated according to community concepts. Data for Belgium-Luxembourg Economic Union were compiled following the national definitions.
Czech Republic, Hungary, Korea, Mexico, Poland, and Slovak republic: are now Members of the OECD and are presented in this publication as reporting countries. With respect to the available historical data, OECD-Total includes respectively Mexico from 1990, Hungary and Poland from 1992, the Czech Republic from 1993, Korea from 1994 and Slovak Republic from 1997.
Germany: Includes Eastern Germany since January 1991;
Partner countries:
Germany: includes Eastern Germany on the whole period;
Switzerland and Liechtenstein: depending on reporter countries, trade with Liechtenstein can be included into Switzerland;
Yugoslavia: From 1992 onwards, no longer exists as such. Its constituent countries are Slovenia, Croatia, Serbia, Bosnia-Herzegovina, Montenegro, and Macedonia.
Czechoslovakia: From 1993 onwards, no longer exists as such and has been split into the Czech Republic and the Slovak Republic.
Concepts & Classifications Concepts & Classifications Aggregation and consolidation Aggregation and consolidationHS is a more detailed classification with 6-digit subheadings even when SITC has 5-digit headings.
Since 1988, OECD receives data according to HS or in a more desegregated level. Data are then converted into SITC Rev. 3 and Rev. 2. From 1991, data may be obtained according to SITC Rev. 2, SITC Rev. 3. From 1996 data may be obtained according to SITC Rev. 2, SITC Rev. 3 HS 96. However, it should be noted that if it is easily feasible to convert data from a recent revision to an older one, the conversion from SITC Rev. 2 to SITC Rev. 3 is quite delicate, if not impossible. Consequently, to obtain a consistent time series, one should carefully choose which revision to use. This is why from 1961 to 1987 data are only available in SITC Rev. 2, which are contained in our Historical Series in SITC Rev. 2 from 1961 to 1990.
The SITC has been regularly revised to take into account the structural changes of the market according to the appearance of new commodities and the need of more detailed statistics on some commodity groups. OECD provides two versions : the SITC Revision 2 and the SITC revision 3. The first version (Revision 1) was introduced in 1960. The second version (SITC Rev. 2) containing 2582 products was introduced and adopted by most Member countries in 1978. The third version (Rev. 3) which contains 4346 produtcs, has been used from 1988 onwards, except the United States and Turkey which have adopted data in Rev. 3 only from 1989 onwards.
An official version of the HS, was instituted in 1988 (HS 88). The HS has been revised in 1996 (HS 1996) and in 2002 (HS 2002) to take into account new trends in the composition of international trade. The HS is broken down by chapter (two-digit) , by heading (four-digit) and by subheading (6 digit). SITC rev. 3 was developed in 1988 in the same way as the HS, this is why it follows the structure of the HS, so that the smallest SITC units are defined by HS subheadings. Since 2002, data are collected according to the HS 2002 and then converted to older classifications, which might affect the allocation of some commodities.
Both classifications, serve the same purpose, namely to provide extensive commodity trade data for instance for : Trade negotiations, monitoring of economic trends, monitoring of various flows of goods, balance of payments, national accounts, market analysis, supply balance sheets, budgetary control.
Transformations TransformationsConfidentiality
OECD Member States generally apply the principle of passive confidentiality; i.e. they take suitable measures at the request of importers or exporters who feel that their interests would be harmed by the dissemination of data. Confidentiality may concern all data relating to a commodity category, or be limited to the breakdown by partner country.
Processing of quantities
Standardisation of quantities is done by country and by year.
The first step in standardisation is to convert the units in which product quantities are reported by a country for a particular year into one of the quantity units used by OECD. The second step concerns the aggregation of product quantities to obtain quantities for product groups. Aggregation is straightforward if the quantity unit is the same for all products covered by product group but, if it is not, further standardisation is required. This standardisation applies not only to the switch from the original nomenclature (e.g. Combined Nomenclature) to the official OECD nomenclature, but also to the transition from a detailed level to a more aggregated level.
Before the implementation of the Joint UN/OECD System (for additional information please refer to the statistical population item), the conversion was carried out using the value/quantity ratio of this product. When quantity units differed within a product group, quantities were converted into the quantity unit of the product with the largest value. The converted product quantities were not published, they were only used in the aggregation process. Consequently, quantities for products or product groups were not necessarily the same neither across countries nor across years.
With the implementation of the Joint UN/OECD System, two quantity fields can be processed: net weight and supplementary quantity unit. Complex calculation rules have been implemented depending on the WCO recommended unit availability, the share of quantity units matching recommended units and the availability of a Standard Unit Value. Additonal details can be provided on demand.
Quantity estimation is one of the main improvments of the Joint UN/OECD System: quantities are now provided according to the WCO recommended units and stable in time and across countries.
Other Aspects Other Aspects Recommended uses and limitations Recommended uses and limitationsFollowing the UN recommendations, the international merchandise trade statistics record all goods which add to or subtract from the stock of material resources of a country by entering (imports) or leaving (exports) its economic territory. Goods simply being transported through a country (goods in transit) or temporarily admitted or withdrawn (except for goods for inward or outward processing) do not add to or subtract from the stock of material resources of a country and are not included in the international merchandise trade statistics.
Customs records should be the main source of the data; and the additional sources could be used where customs sources are not available. Goods should be included in statistics at the time when they enter or leave the economic territory of a country. In the case of customs-based data collection systems, the time of recording should be the date of lodgement of the customs declaration.
Lists of goods to be included, and recorded separately, and to be excluded should be provided. Specific goods are to be excluded from detailed international merchandise trade statistics but recorded separately in order to derive totals of international merchandise trade for national accounts and balance of payments purposes.
In European countries, two systems of data collection coexist i.e. Extra-stats and Intrastat. Extra-EU trade statistics record movable property imported and exported by the EU Member country with countries outside the European community. Intra-EU trade statistics record the arrival and dispatch of movable goods within the European community recorded by each Member state of the EU.
For exceptions and for definitions of statistical territories, please see country notes.
Differences between national OECD statistics and Community statistics of Eurostat
ITCS now publishes data received directly from the Statistical Office of the European Communities (Eurostat) under the name EU15 - Extra EU which excludes Intra EU trade.
As the example below shows, European External Trade Statistics which cover the European Union as a whole and the statistics compiled by the EU Member States and sent to OECD, which are concerned with the national dimension, are not always directly comparable. There can be methodological differences, which make comparison of these statistics impossible.
The principal differences are as follows :
Breakdown by partner country
For arrivals of goods from other EU Member States, certain EU Member States record the country of origin as the partner country, whereas the EU Member State of consignment appears in Community statistics relating to the same movements.
Treatment of goods in transit
Some EU Member States, particularly the Netherlands, does not record goods, which they consider to be 'in transit'. This involves, firstly, imports from non-member countries which are cleared in these EU Member States before being dispatched to other EU Member States and, secondly, goods from other EU Member States which are immediately re-exported to non-member countries.
These goods are normally recorded under intra- or extra-EU trade, as appropriate. This phenomenon is known as the 'Rotterdam effect'.
Other differences
Other methodological differences can cause discrepancies between national statistics received by OECD and Community statistics (examples: classification at national level as 'general trade' rather than 'special trade', or not recording repairs on the grounds that they are services).
Example :
Japanese goods are imported into Europe; they are released for free circulation in Germany, then dispatched to France (EU Member State of consumption). For such an operation, the various recordings will be as follows:
For European statistics, three operations are recorded:
- import of goods originating in Japan (with Germany as the declaring Member State, since the customs declaration is made there);
- dispatch (intra) from Germany to France;
- arrival (intra) in France from Germany.
For German national statistics, no trade is recorded, as the import from Japan and dispatch to France is regarded as transit.
For French national statistics, goods originating in Japan are entered as imports. France records Japan as the country of origin, as indicated on the Intrastat declaration. This information is considered statistically more relevant at national level.
Quality comments Quality commentsIntrastat
Concerning EU member countries, the advent of the Single Market 1 January 1993 with its removal of customs formalities (the traditional source of statistical data) between Member States leads to the adoption of a specially designed collection system, Intrastat, for statistics on intra-Community trade. These changes necessitate greater vigilance on the part of statistical users because they obviously affect the nature, quality and coverage of the data. In particular, the introduction of Intrastat in 1993 involved a methodological break with the past and affected the quality of the statistics.
Other comments Other commentsTrade statistics are used for many data and economic analysis. Here are some examples of use of ITCS data.
Bilateral Trade Database
STAN Bilateral Trade Database (BTD) shows trade flows broken down by reporter country, partner country (or economic/ geographical zone) and economic activity. In BTD, the list of industries is based on the ISIC Revision 3 and is compatible with the industry lists used in other STAN family databases. The data have been converted from the OECD's International Trade by Commodity Statistics (ITCS) and are presented in US dollars, at current prices.
OECD International Trade Indicators
The OECD International Trade Indicators database brings separate databases together in one application to provide cross-disciplinary background information for globalization analysis purposes (with particular emphasis on trade aspects). It contains macro and micro trade indicators for the 30 OECD member countries. Trade indicators on aggregated level (total trade, trade of goods, trade of services) are provided in current and constant prices. Trade indicators on detailed (chapter/section) level (total trade, trade of goods, trade of services) are provided in current prices by type of goods, by type of industry or by category of service.
Tariffs and Trade database
The CD ROM, Tariffs and Trade (T&T) provides trade negotiators with a useful tool that will help them formulate their negotiating objectives and strategies in the area of tariffs; it also provides them with key data that are necessary to define negotiating scenarios and impute the corresponding impact on trade, employment and growth. It provides a unique and comprehensive data set on market access issues that includes detailed, line-by-line information on tariffs and trade flows.
Specific terms and conditions apply to the use of these data: http://comtrade.un.org/db/help/LicenseAgreement.aspx
Values are expressed in current USD. Users of OECD's International Trade Statistics databases should note that since February 2002, the national exchange rates for the Euro area countries have been converted into euros.
The option chosen by OECD is to convert exchange rates for periods prior to entry into European Monetary Union (EMU), i.e. prior to 1999 for all members apart from Greece, which acceded in 2001, from the former national currency exchange rate using the appropriate irrevocable exchange rate. Such a conversion facilitates comparisons over time within a country and also preserves the historical evolution (i.e. growth rates). However, pre-EMU euro rates are notional units and are not always suitable to form area aggregates or for cross country comparisons. For further details, see The Statistics Brief Number 2, February 2002.
Quantity units are: Area in square metres, Electrical energy in thousands of kilowatt-hours, Length in meters Longueur en mètres, Number of items, Number of pairs, Volume in liters, Weight in kilograms, Thousands of items, Number of packages, Dozen of items, Volume in cubic meters, Weight in carats.
Partner country: 280 individual areas are presented in ISO codes or in long label. Economic and geographic country groups are also presented. The geonomenclature is available online.
Flow: Imports, Exports, Re-imports and Re-exports.
Time: From 1961 depending on countries and classifications.
Notes that can be attached to data are: Estimated Value, Includes not available Value for products at lower level, Includes not available Value for detailed partners, Estimated net Weight, Estimated Quantity, Includes not available Quantity for products at lower level, Includes not available Quantity for detailed partners.
The OECDInternational Trade by Commodity Statistics database contains values and quantities of exports and imports by partner countries and by commodity or industry. Commodities are available at the most detailed level of the SITC (Revision 2 and 3) and the Harmonised System (HS 1988, HS 1996, HS 2002 and HS 2007).
The database dimensions are: reporter country, partner country, commodity, year, flow and value and quantity.
Thejoint OECD-UN Trade Data Collection and Processing System
The OECD and the United Nation Statistics Division (UNSD) have been working together during the past years to agree on the best statistical treatments of all aspects relating to international trade data and to align their respective data processing practices. Additional information on methodological changes is available in the online document The new and Operational UNSD-OECD Joint Trade Data Collection and Processing System, Methodological Issues.
Both organisations have identical data since 2005 and are also progressively aligning their historical data. The result is an improvement of data quality and data consistency.
The OECD Merchandise Trade Statistics Geonomenclature presents the components of the main economic and geographic zones as well as the detailed statistical territories. All detailed components are also available in Excel format.
Reporting countries:
Belgium-Luxembourg Economic Union: Since 1999, Belgium and Luxembourg henceforth publish separate foreign trade results. Belgium-Luxembourg Economic Union statistics are available from 1961 to 1992. Belgium data are available since 1993, while for Luxembourg, which can not provide historical data, data are available since 1999.
Belgium's statistics and Luxembourg's statistics are elaborated according to community concepts. Data for Belgium-Luxembourg Economic Union were compiled following the national definitions.
Czech Republic, Hungary, Korea, Mexico, Poland, and Slovak republic: are now Members of the OECD and are presented in this publication as reporting countries. With respect to the available historical data, OECD-Total includes respectively Mexico from 1990, Hungary and Poland from 1992, the Czech Republic from 1993, Korea from 1994 and Slovak Republic from 1997.
Germany: Includes Eastern Germany since January 1991;
Partner countries:
Germany: includes Eastern Germany on the whole period;
Switzerland and Liechtenstein: depending on reporter countries, trade with Liechtenstein can be included into Switzerland;
Yugoslavia: From 1992 onwards, no longer exists as such. Its constituent countries are Slovenia, Croatia, Serbia, Bosnia-Herzegovina, Montenegro, and Macedonia.
Czechoslovakia: From 1993 onwards, no longer exists as such and has been split into the Czech Republic and the Slovak Republic.
HS is a more detailed classification with 6-digit subheadings even when SITC has 5-digit headings.
Since 1988, OECD receives data according to HS or in a more desegregated level. Data are then converted into SITC Rev. 3 and Rev. 2. From 1991, data may be obtained according to SITC Rev. 2, SITC Rev. 3. From 1996 data may be obtained according to SITC Rev. 2, SITC Rev. 3 HS 96. However, it should be noted that if it is easily feasible to convert data from a recent revision to an older one, the conversion from SITC Rev. 2 to SITC Rev. 3 is quite delicate, if not impossible. Consequently, to obtain a consistent time series, one should carefully choose which revision to use. This is why from 1961 to 1987 data are only available in SITC Rev. 2, which are contained in our Historical Series in SITC Rev. 2 from 1961 to 1990.
The SITC has been regularly revised to take into account the structural changes of the market according to the appearance of new commodities and the need of more detailed statistics on some commodity groups. OECD provides two versions : the SITC Revision 2 and the SITC revision 3. The first version (Revision 1) was introduced in 1960. The second version (SITC Rev. 2) containing 2582 products was introduced and adopted by most Member countries in 1978. The third version (Rev. 3) which contains 4346 produtcs, has been used from 1988 onwards, except the United States and Turkey which have adopted data in Rev. 3 only from 1989 onwards.
An official version of the HS, was instituted in 1988 (HS 88). The HS has been revised in 1996 (HS 1996) and in 2002 (HS 2002) to take into account new trends in the composition of international trade. The HS is broken down by chapter (two-digit) , by heading (four-digit) and by subheading (6 digit). SITC rev. 3 was developed in 1988 in the same way as the HS, this is why it follows the structure of the HS, so that the smallest SITC units are defined by HS subheadings. Since 2002, data are collected according to the HS 2002 and then converted to older classifications, which might affect the allocation of some commodities.
Both classifications, serve the same purpose, namely to provide extensive commodity trade data for instance for : Trade negotiations, monitoring of economic trends, monitoring of various flows of goods, balance of payments, national accounts, market analysis, supply balance sheets, budgetary control.
Confidentiality
OECD Member States generally apply the principle of passive confidentiality; i.e. they take suitable measures at the request of importers or exporters who feel that their interests would be harmed by the dissemination of data. Confidentiality may concern all data relating to a commodity category, or be limited to the breakdown by partner country.
Processing of quantities
Standardisation of quantities is done by country and by year.
The first step in standardisation is to convert the units in which product quantities are reported by a country for a particular year into one of the quantity units used by OECD. The second step concerns the aggregation of product quantities to obtain quantities for product groups. Aggregation is straightforward if the quantity unit is the same for all products covered by product group but, if it is not, further standardisation is required. This standardisation applies not only to the switch from the original nomenclature (e.g. Combined Nomenclature) to the official OECD nomenclature, but also to the transition from a detailed level to a more aggregated level.
Before the implementation of the Joint UN/OECD System (for additional information please refer to the statistical population item), the conversion was carried out using the value/quantity ratio of this product. When quantity units differed within a product group, quantities were converted into the quantity unit of the product with the largest value. The converted product quantities were not published, they were only used in the aggregation process. Consequently, quantities for products or product groups were not necessarily the same neither across countries nor across years.
With the implementation of the Joint UN/OECD System, two quantity fields can be processed: net weight and supplementary quantity unit. Complex calculation rules have been implemented depending on the WCO recommended unit availability, the share of quantity units matching recommended units and the availability of a Standard Unit Value. Additonal details can be provided on demand.
Quantity estimation is one of the main improvments of the Joint UN/OECD System: quantities are now provided according to the WCO recommended units and stable in time and across countries.
Following the UN recommendations, the interna­tional merchandise trade statistics record all goods which add to or subtract from the stock of material re­sources of a country by entering (imports) or leaving (exports) its economic territory. Goods simply being transported through a country (goods in transit) or tem­porarily admitted or withdrawn (except for goods for inward or outward processing) do not add to or subtract from the stock of material resources of a country and are not included in the international merchandise trade statistics.
Customs records should be the main source of the data; and the additional sources could be used where customs sources are not available. Goods should be in­cluded in statistics at the time when they enter or leave the eco­nomic territory of a country. In the case of cus­toms-based data collection systems, the time of recording should be the date of lodgement of the cus­toms decla­ration.
Lists of goods to be included, and recorded sepa­rately, and to be excluded should be provided. Specific goods are to be excluded from detailed international merchan­dise trade statistics but recorded separately in order to derive totals of international merchandise trade for na­tional accounts and balance of payments pur­poses.
In European coun­tries, two systems of data collection coexist i.e. Ex­tra-stats and Intrastat. Extra-EU trade statistics record movable property imported and exported by the EU Member country with countries outside the European community. Intra-EU trade statistics record the arrival and dispatch of movable goods within the European commu­nity recorded by each Member state of the EU.
For exceptions and for defi­nitions of statistical territories, please see country notes.
Differences between national OECD statistics and Community statistics of Eurostat
ITCS now publishes data received directly from the Statistical Office of the European Communities (Eurostat) under the name EU15 - Extra EU which excludes Intra EU trade.
As the example below shows, European External Trade Statistics which cover the European Union as a whole and the statistics compiled by the EU Member States and sent to OECD, which are concerned with the national dimension, are not always directly comparable. There can be methodological differences, which make comparison of these statistics impossible.
The principal differences are as follows :
Breakdown by partner country
For arrivals of goods from other EU Member States, certain EU Member States record the country of origin as the partner country, whereas the EU Member State of consignment appears in Community statistics relating to the same movements.
Treatment of goods in transit
Some EU Member States, particularly the Netherlands, does not record goods, which they consider to be 'in transit'. This involves, firstly, imports from non-member countries which are cleared in these EU Member States before being dispatched to other EU Member States and, secondly, goods from other EU Member States which are immediately re-exported to non-member countries.
These goods are normally recorded under intra- or extra-EU trade, as appropriate. This phenomenon is known as the 'Rotterdam effect'.
Other differences
Other methodological differences can cause discrepancies between national statistics received by OECD and Community statistics (examples: classification at national level as 'general trade' rather than 'special trade', or not recording repairs on the grounds that they are services).
Example :
Japanese goods are imported into Europe; they are released for free circulation in Germany, then dispatched to France (EU Member State of consumption). For such an operation, the various recordings will be as follows:
For European statistics, three operations are recorded:
- import of goods originating in Japan (with Germany as the declaring Member State, since the customs declaration is made there);
- dispatch (intra) from Germany to France;
- arrival (intra) in France from Germany.
For German national statistics, no trade is recorded, as the import from Japan and dispatch to France is regarded as transit.
For French national statistics, goods originating in Japan are entered as imports. France records Japan as the country of origin, as indicated on the Intrastat declaration. This information is considered statistically more relevant at national level.
Intrastat
Concerning EU member countries, the advent of the Single Market 1 January 1993 with its removal of customs formalities (the traditional source of statistical data) between Member States leads to the adoption of a specially designed collection system, Intrastat, for statistics on intra-Community trade. These changes necessitate greater vigilance on the part of statistical users because they obviously affect the nature, quality and coverage of the data. In particular, the introduction of Intrastat in 1993 involved a methodological break with the past and affected the quality of the statistics.
Trade statistics are used for many data and economic analysis. Here are some examples of use of ITCS data.
Bilateral Trade Database
STAN Bilateral Trade Database (BTD) shows trade flows broken down by reporter country, partner country (or economic/ geographical zone) and economic activity. In BTD, the list of industries is based on the ISIC Revision 3 and is compatible with the industry lists used in other STAN family databases. The data have been converted from the OECD's International Trade by Commodity Statistics (ITCS) and are presented in US dollars, at current prices.
OECD International Trade Indicators
The OECD International Trade Indicators database brings separate databases together in one application to provide cross-disciplinary background information for globalization analysis purposes (with particular emphasis on trade aspects). It contains macro and micro trade indicators for the 30 OECD member countries. Trade indicators on aggregated level (total trade, trade of goods, trade of services) are provided in current and constant prices. Trade indicators on detailed (chapter/section) level (total trade, trade of goods, trade of services) are provided in current prices by type of goods, by type of industry or by category of service.
Tariffs and Trade database
The CD ROM, Tariffs and Trade (T&T) provides trade negotiators with a useful tool that will help them formulate their negotiating objectives and strategies in the area of tariffs; it also provides them with key data that are necessary to define negotiating scenarios and impute the corresponding impact on trade, employment and growth. It provides a unique and comprehensive data set on market access issues that includes detailed, line-by-line information on tariffs and trade flows.