A new study said nearly a quarter of the nation's illegal immigrants live in California.
A Pew Hispanic Center report released Wednesday also said illegal immigrants comprise 6.9 percent of California's population -- the highest percentage in the country.
Overall, the number of illegal immigrants in the United States has dropped for the first time in 20 years, with California housing 23 percent of the country's 11.1 million immigrants.
The study also says 9.3 percent of California's workforce is illegal labor - second highest in the nation.
The study, based on 2009 statistics, did not include California comparisons to earlier years.
New York Mayor Michael Bloomberg, an outspoken advocate of welcoming more immigrants to the U.S., said he was not surprised by the study's findings.
"It exemplifies what I've been saying all along," Bloomberg told reporters. "Not totally, but generally, people come here from around the world -- whether they come here legally or illegally -- to work, to build a better life for themselves and for their families. And when our economy is down, it's just tougher to get a job."
Other Pew findings:
- The states with the highest percentage of illegal immigrants were California (6.9 percent), Nevada (6.8 percent), Texas (6.5 percent) and Arizona (5.8 percent). The numbers are expected to play an important factor in whether those states lose or gain fewer U.S. House seats than expected after the 2010 census.
- Illegal immigrants make up about 28 percent of the foreign-born population in the U.S., down from 31 percent in 2007.
- The unemployment rate for illegal immigrants in March 2009 was 10.4 percent -- higher than that of U.S.-born workers or legal immigrants, who had unemployment of 9.2 percent and 9.1 percent, respectively.