South Korea kept a trade surplus for 80 months through September despite a decline in export, caused by less business days, customs data showed Monday.

The revised data for trade surplus was 9.6 billion U.S. dollars in September, staying in the black for 80 months since February 2012, according to Korea Customs Service.

Export, which accounts for about half of the export-driven economy, shrank 8.2 percent over the year to 50.6 billion dollars in September, but it topped 50 billion dollars for the fifth consecutive month.

The September fall came as the Chuseok holiday, the South Korean version of Thanksgiving Day, reduced working days. Excluding the working day effect, the daily average export hit a new high of 2.59 billion dollars last month.

For the first nine months of this year, the export reached a fresh record high of 450.3 billion dollars.

Import shed 1.6 percent from a year earlier to 41 billion dollars in September.

Exports for semiconductors and oil products posted a double-digit increase last month, but those for automobiles, ships and telecommunications devices, including smartphones, declined by a double-digit.

Imports for crude oil and natural gas jumped on higher prices, but those for machinery and automobiles declined last month.