WASHINGTON — Big gains in exports and overseas investment income narrowed the United States’ current-account deficit in the fourth quarter to the lowest level in 14 years.

The imbalance fell to $81.1 billion in the October-December quarter, down from $96.4 billion in the July-September quarter, the Commerce Department said on Wednesday. That is the smallest gap since the third quarter of 1999.

The current account is the country’s broadest measure of trade, covering not only goods and services, but also investment flows. A smaller trade deficit usually means that American companies are producing more to meet domestic and overseas demand.

Goods exports rose 1.9 percent to $405.4 billion, driven by higher overseas sales of petroleum and agricultural products.