The geographic seasonal adjustments are developed and applied directly at the country and world area level. This differs from seasonal adjustments in other BEA and Census Bureau data on trade in goods and services, which are applied to detailed end-use commodity data for goods and to detailed service-type data for services.
The seasonal adjustment procedure (X-13ARIMA-SEATS) is based on a model that estimates the period-to-period movements as percentages above or below the general level of each series (unlike other methods that redistribute the actual series values over the calendar year).