Items not considered as imports and exports include: Shuttle trade, transit trade, temporary trade, goods for and after repair and maintenance, operational leasing monetary gold and transactions under $100.
Geographical coverage: Geographical coverage is based on customs boundaries. Statistical territory is the custom territories except free zones and warehouses.
Unrecorded activity: Data on shuttle trade are not included. Although TURKSTAT and the Central Bank of Turkey makes estimates on shuttle trade for balance of payments data, these are not included in the foreign trade figures disseminated by TURKSTAT.
· Valuation: Exports are valued free on board (FOB) and imports on cost, insurance and freight (CIF).
Sources: Main data source is customs declarations. Data of electricity, natural gas and crude petroleum is received from enterprises.
Basis of country data: Country of origin for imports and country of last known destination for exports.
In the January-June press releases data of previous and current year, in the July-December press releases only data of current year is published, temporarily.
Geographic detail: The data are available by province, country of origin (for imports) and country of final destination (for exports). A breakdown by country groups is also available.
Commodity detail: The data are available in HS 12-digit.
Seasonal and calendar adjustment: Seasonal and calendar related effects prevent observing the general tendency of data because of their temporary characteristics. Therefore, identification of seasonal patterns of short term indicators plays crucial role in order to make reliable comparisons between consecutive periods.
The seasonal adjustment of Foreign Trade Statistics is carried out using TRAMO-SEATS methodology. The software that is used for the application of this method is 2.2.0 version of JDemetra+ developed by the National Bank of Belgium (NBB) in cooperation with the Deutsche Bundesbank and Eurostat in accordance with the Guidelines of the European Statistical System.
Seasonal Adjustment Process
Seasonal and calendar adjustment process of Foreign Trade Statistics begins at the end of each year with the identification of the models of next year. This specified model structure is kept fixed throughout the year to adjust seasonally and/or calendar effects. At the end of the year, just like the previous year, specification of econometric estimation models for the following year is done. The identified process repeats itself in a cyclical manner each year.
While 20 subtitles of Foreign Trade series contain both seasonal and calendar effects, 4 subtitles contain neither of these effects, 4 subtitles include only calendar effects.
Direct or Indirect Seasonal Adjustment
Seasonally and calendar adjusted figures of total exports and imports are produced by indirect approach. The individual subtitles of Foreign Trade series by SITC and BEC classification are seasonally adjusted and then aggregated to derive seasonally and calendar adjusted totals. The indirect approach has the advantage of easy calculation of contributions to growth from components of main aggregates and advantage of retaining additivity.
Seasonal adjustment procedure is subject to revisions over time because of the re-estimation of seasonal component as new observations are added. These revisions are implemented on the data of the last three years excluding the current year.
Adjusted data has been published in 3 different ways.
“Calendar adjusted” data is derived from unadjusted data by removing calendar and holiday originated effects. Calendar adjusted data should be used in comparisons regarding the same month/period of the previous year.
“Seasonally adjusted” data is derived from unadjusted data by removing effects originating from seasonal effects. Seasonally adjusted data should be used in comparisons regarding the previous month/period.
If unadjusted data contains both calendar and holiday, and seasonal effects, “seasonally and calendar adjusted” data is derived by removing these effects. Seasonally and calendar adjusted data should be used in comparisons regarding the previous month/period.
Province data: Trade by province is prepared according to the province where the head office of firm is located in. The main data source of business registers is the Revenue Administration Department’s registers. In addition, for the enterprises having more than 20 employees full enumeration method is used. Provinces of head office can be change year by year. This situation sould be considered while comparing the data from year to year.