Trade unions are much weaker than they once were, while the buying power of the minimum wage is at a 50-year low. And health care is far more expensive than it was a decade ago, causing companies to spend more on benefits at the expense of wages.

Together, these forces have caused a growing share of the economy to go to companies instead of workers’ paychecks. In the first quarter of 2006, wages and salaries represented 45 percent of gross domestic product, down from almost 50 percent in the first quarter of 2001 and a record 53.6 percent in the first quarter of 1970, according to the Commerce Department. Each percentage point now equals about $132 billion.

Total employee compensation — wages plus benefits — has fared a little better. Its share was briefly lower than its current level of 56.1 percent in the mid-1990’s and otherwise has not been so low since 1966.

Over the last year, the value of employee benefits has risen only 3.4 percent, while inflation has exceeded 4 percent, according to the Labor Department.

In Europe and Japan, the profit share of economic output is also at or near record levels, noted Larry Hatheway, chief economist for UBS Investment Bank, who said that this highlighted the pressures of globalization on wages. Many Americans, be they apparel workers or software programmers, are facing more comptition from China and India.

In another recent report on the boom in profits, economists at Goldman Sachs wrote, “The most important contributor to higher profit margins over the past five years has been a decline in labor’s share of national income.” Low interest rates and the moderate cost of capital goods, like computers, have also played a role, though economists note that an economic slowdown could hurt profits in coming months.

For most of the last century, wages and productivity — the key measure of the economy’s efficiency — have risen together, increasing rapidly through the 1950’s and 60’s and far more slowly in the 1970’s and 80’s.