The U.S. economy contracted slightly more than previously estimated in the fourth quarter, pulled down by falling consumer spending and exports, while corporate profits plunged by the biggest margin since 1994, government data showed on Thursday.

Gross domestic product, which measures the total output of goods and services within U.S. borders, fell at an annual rate of 6.3 percent in the October-December quarter, the steepest decline since the first quarter of 1982, the department said.

The government last month estimated the fall in fourth-quarter GDP at 6.2 percent and the modest revisions to the output estimates reflected adjustments to business inventories and investment figures.

Analysts had forecast fourth-quarter GDP contracting by 6.5 percent. The economy expanded 1.1 percent in 2008, the smallest advance since 2001, after growing 2.0 percent in the prior year, the department said.

Private business inventories were revised to show a $25.8 billion decline, previously reported as a $19.9 billion fall, as business responded to the slump in demand by cutting output.

Business investment, which is typically made when companies are planning production increases, fell at a 21.7 percent rate, the biggest fall since the first quarter of 1975, from a previously estimated 21.1 percent contraction. Residential investment fell 22.8 percent in the fourth quarter.

Consumer spending, which accounts for more than two-thirds of domestic economic activity, dropped a 4.3 percent rate, unchanged from last month's estimates.

Exports were down 23.6 percent, also unrevised from last month's report.

The department said corporate profits after taxes plummeted by 10.7 percent, the biggest decline since the first quarter of 1994. Analysts polled by Reuters had forecast corporate profits sliding by 2.0 percent in the fourth quarter.

(Reporting by Lucia Mutikani, Editing by Andrea Ricci)