The proportion of immigrants employed in the U.S. is at the highest level in seven decades, the Bureau of Labor Statistics reports. Experts say that immigrants are expected to continue to spread throughout the U.S. economy -- and their impact will intensify in coming years.

• The number of immigrant workers jumped to 15.7 million last year -- up 17 percent from three years earlier.

• Some five million immigrant workers are in the U.S. illegally.

• Under existing quotas, about 800,000 immigrants enter the country legally each year -- with another 300,000 coming in illegally.

• Immigrants dominate dozens of types of employment -- poultry plant workers, meat packers, gardeners, hotel maids, seamstresses, restaurant workers, building demolition workers and fruit and vegetable pickers.

While labor unions continue to fight efforts to allow hundreds of thousands of additional immigrants to enter legally each year, they have softened their opposition -- and are beginning to turn their attention to unionizing the new arrivals.

Salaries of the immigrant workers range from an illegally low $3 an hour for supermarket deliverers to $100,000 or more for software developers from India.

A study by the National Academy of Sciences found that immigrants -- especially the illegal, and unskilled from Mexico and the rest of Latin America -- have pushed down wages for American-born workers with less than a high school education by 5 percent.

Source: Steven Greenhouse, "Foreign Workers at Highest Level in Seven Decades," New York Times, September 4, 2000.