U.S. multinational corporations, the big brand-name companies that employ a fifth of all American workers, have been hiring abroad while cutting back at home, sharpening the debate over globalization's effect on the U.S. economy.

The companies cut their work forces in the U.S. by 2.9 million during the 2000s while increasing employment overseas by 2.4 million, new data from the U.S. Commerce Department show. That's a big switch from the 1990s, when they added jobs everywhere: 4.4 million in the U.S. and 2.7 million abroad.

In all, U.S. multinationals employed 21.1 million people at home in 2009 and 10.3 million elsewhere, including increasing numbers of higher-skilled foreign workers.

The trend highlights the growing importance of other economies, particularly in rapidly growing Asia, to big U.S. businesses such as General Electric Co. , Caterpillar Inc., Microsoft Corp. and Wal-Mart Stores Inc.

The data also underscore the vulnerability of the U.S. economy, particularly at a time when unemployment is high and wages aren't rising. Jobs at multinationals tend to pay above-average wages and, for decades, sustained the American middle class.