The commission attributed the 40 percent increase, equal to 1,292 people, partially to better methodology used to take an accurate count but mostly to the jobs lost during the recession.

The commission released its Homeless Census and Survey results Tuesday at the county Board of Supervisors meeting.

The 4,539 homeless people counted in January represents 2.6 percent of the county's population of 483,878, the commission said.

Three-quarters of the homeless were unsheltered, and 22 percent were chronically homeless, according to the report.

People who experience chronic homelessness are defined as individuals 18 or older with a disabling condition or a family with at least one adult with a disabling condition who have been homeless for a year or more or have had four or more episodes of homelessness within the past three years.

There were 701 unaccompanied homeless youth under 24 years old - 264 who were under age 18 -- and 28 percent of them said they tried to stay at an emergency shelter within the past 30 days but were turned away.

Supervisor Shirlee Zane said that statistic was "terrifying and heart breaking."

"We're sheltering animals in this county. There's something wrong with this picture," Zane said.

The majority of the homeless are white males between ages 31 and 60, and 75 percent of the 617 people who answered a survey said they were living in Sonoma County when they most recently became homeless, according to the report.

That debunks the suspicion that homeless people relocate to Sonoma County for its social services network, said Peter Connery, a consultant for Applied Survey Research, the San Jose company that conducted the survey.

The number of homeless people decreased between 2009 and 2011 in the north county, stayed about the same in the west county and increased in the south county, Sonoma Valley and in central Santa Rosa.

One-third of the 617 survey respondents said they were homeless because of a job loss, and 16 percent said drug use, alcohol use, or both led to their homelessness, according to the report.

Fifty-five percent of those who took the survey said it was the first time they were homeless, and two-thirds of the respondents said they were receiving one or more forms of government assistance.

Supervisors Efren Carrillo, David Rabbitt and Mike McGuire called the report "sobering," "heart breaking" and "shocking."

Zane said the county "is not doing enough" for the homeless and that she will make the issue a priority during the 2011-2012 budget review process.