Revisions to international merchandise trade statistics
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Quarterly international merchandise trade statistics are published approximately six weeks after the reference period. Two weeks later, these data are incorporated into the Income and Expenditure Accounts, at which point they are subject to revision. This note outlines the primary sources of the revisions.
As an example, Table 1 presents current and constant dollar revisions to international merchandise trade from the original estimates to the subsequent quarterly merchandise trade estimates contained in the Income and Expenditure Accounts for the past five quarters.
Current dollar revisions
In current dollars, the revisions are often due to revisions to energy data, made after the quarterly international merchandise trade statistics have been published. For exports of crude oil and natural gas, and imports of crude oil, there are two sources of volume information, namely customs data and the energy survey1 data. The energy survey data better reflect the month in which the transactions occur and are also consistent with other energy survey data on supply and demand. However, not all the energy survey data are available in time for the quarterly publication of international Merchandise Trade Statistics. When the Income and Expenditure Accounts are being calculated, more up-to-date energy survey data become available and are included in the estimates of international merchandise trade and gross domestic product (GDP). Table 2 shows all the current and constant dollar differences for energy trade for the past five quarters.
In addition to more timely energy data, there may be revisions to the published quarterly international Merchandise Trade Statistics arising from the balancing of the quarterly Income and Expenditure Accounts or the availability of revised customs data. Furthermore, in the first quarter of the year, there are revisions to Income and Expenditure Accounts international trade data arising from the four-year annual revision of the national accounts. These primarily include revised seasonal patterns and new estimates for under-coverage of exports. The release of the Income and Expenditure Accounts' four year revision precedes the revision of the quarterly international Merchandise Trade Statistics by a couple of weeks, when similar data are published.
Constant dollar revisions
The above mentioned current dollar revisions are also reflected in the constant dollar international merchandise trade statistics published in the quarterly Income and Expenditure Accounts. However, in the constant dollar series, there are additional revisions arising from changes to the adjustments made to trade price indexes, which are captured in the 'other balance of payments adjustments ' trade series. The differences between the series are shown in Table 3.
Table J.3 Difference between the monthly international Merchandise Trade Statistics and the quarterly Income and Expenditure Accounts international Merchandise Trade Statistics: other balance of payments adjustments
Aaggregate international trade price adjustments are re-calculated during the quarterly production of the Income and Expenditure Accounts, as relevant information becomes available. The adjustments included during the production of the monthly international merchandise trade statistics are typically forecasts based on historical rates and at times can differ from final values derived when more complete information becomes available.
Finally, an important part of the construction of the Income and Expenditure Accounts is an extensive economy-wide coherence analysis through supply and disposition models and comparisons between data sources - exports and production for example. At times, based on this analysis it is necessary to adjust international merchandise trade either at the commodity or aggregate level.
Note:1. Crude oil production data are provided by the producing provinces through: Crude Oil and Natural Gas Monthly; crude oil exports are picked up from our pipeline survey: Monthly Oil Pipeline Survey; crude oil imports from the Monthly Supply and Disposition of Refined Petroleum Products Survey; natural gas exports: partially from the National Energy Board; and natural gas exports data from the monthly Gas Utilities/Transportation and Distribution Systems.
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