Nearly one in six American workers is foreign-born, the highest proportion since the 1920s, according to a census analysis released Monday.

Because of government barriers to immigration, the share of foreign-born workers dipped from a 20th-century high of 21 percent in 1910 to barely 5 percent in 1970, but has been rising since then, to the current 16 percent.

In 2007, immigrants accounted for more than one in four workers in California (35 percent), New York (27 percent), New Jersey (26 percent) and Nevada (25 percent).

For the first time, the Census Bureau also compared immigrants by generation. Generally, income and other measures of achievement rose from one generation to the next, although educational attainment peaked with the second generation.