Washington (CNN) -- The number of unauthorized immigrants in the United States decreased by 800,000 from 2008 to 2009, the Department of Homeland Security said in a report released Wednesday.
There were 11.6 million unauthorized immigrants in the United States in January 2008 and 10.8 million one year later, DHS said. The decrease in the number of immigrants coincided with the U.S. economic downturn, the report said.
A Pew Hispanic Center report in July noted that the recession has had a harsh impact on employment of immigrants.
Nearly two of every three unauthorized immigrants came from Mexico, DHS said.
Of all unauthorized immigrants living in the United States in 2009, 63 percent entered before 2000, according to the report.
The report said there were 10.5 million unauthorized immigrants in the United States in 2005, 11.3 million in 2006 and 11.8 million in 2007.
The Pew Hispanic Center shows 11.9 million unauthorized immigrants in March 2008, 12.4 million in March 2007, 11.5 million in March 2006 and 11.1 million in March 2005.
Jeanne Batalova, a policy analyst at the independent Migration Policy Institute, agreed with the Pew Center's conclusion that the decline is caused primarily by the economic downturn.
Unauthorized entry into the United States frequently "requires cash and entails significant risk in terms of life and safety," she told CNN. "The calculus has changed. It's not worth taking that chance right now."
Batalova also cited tighter border controls and increased immigration enforcement among employers as contributing factors to the drop.
An estimated 8.5 million of the total 10.8 million unauthorized immigrants living in the United States in 2009 were from the North America region, including Canada, Mexico, the Caribbean and Central America, the DHS report said. The next leading regions were Asia with 980,000 and South America with 740,000.
There were 6.7 million unauthorized immigrants from Mexico in 2009, representing 62 percent of the unauthorized population, the report said. The next leading sources for unauthorized immigrants last year were El Salvador (530,000), Guatemala (480,000), Honduras (320,000) and the Philippines (270,000).
Between 2000 and 2009, the unauthorized immigrant population from Mexico increased by 2 million, or 42 percent. The greatest percentage increases occurred among unauthorized immigrants from Honduras (95 percent), Guatemala (65 percent) and India (64 percent).
California remained the leading state in the number of unauthorized immigrants in 2009, with 2.6 million. Next came Texas with 1.7 million, Florida with 720,000, New York with 550,000 and Illinois with 540,000.
California's share of the national total was 24 percent in 2009, compared with 30 percent in 2000. The greatest percentage increases in the unauthorized population between 2000 and 2009 occurred in Georgia (115 percent), Nevada (55 percent) and Texas (54 percent).
In 2009, 61 percent of unauthorized immigrants were ages 25 to 44, and 58 percent were male. Males accounted for 62 percent of the unauthorized population in the 18 to 34 age group in 2009, while females accounted for 52 percent of the 45 and older age segment.