View the photo gallery: Homeless in San Diego

The homeless population in San Diego city and county is now the fourth largest in the country, according to new data from the U.S. Department of Housing and Urban Development, and nearly 48 percent of them are sleeping on the streets.

San Diego’s homeless population rose to 8,742 this year from 8,506 in 2014, a 2.8 percent increase that bumped it into the top four for the first time behind the metropolitan areas of Seattle, Los Angeles and New York City.

San Diego was the 12th ranked metro area in 2007, and has steadily made its way up to the No. 4 spot, according to the federal data.

San Diego’s homeless population has fallen from a peak in 2010 of 10,013, but other areas have made more rapid progress in addressing homelessness, resulting in the higher ranking for San Diego.

The data also shows Las Vegas increasing in rank, coming in at No. 5. Meanwhile, cities including Denver and Houston have fallen out of the top 10 — both of which used to have more homeless people than San Diego.

The data comes from HUD’s annual homeless assessment report to Congress, which is primarily based off street counts conducted in late January of each year.

Dolores Diaz, executive director of the Regional Task Force on the Homeless, which conducts the January count each year, said a number of factors influence San Diego’s homeless population and it’s hard to pinpoint an exact explanation for this year’s spike.

According to the most recent Regional Task Force count, one-fifth of the homeless population reported having a severe mental illness and 17 percent reported substance or alcohol abuse disabilities.

It’s hard to choose what programs will be the most effective when there are a variety of causes, said San Diego Housing Commission President and CEO Richard Gentry.

“There’s no one solution to a problem that’s caused by a number of factors,” Gentry said. “Some just need shelter. Others need a variety of services.”

The commission has launched a number of long- and short-term assistance programs to reduce homelessness in the area. Some focus on providing treatment for behaviors that contribute to homelessness such as drug abuse and mental illness.

Gentry said other programs focus solely on providing affordable housing to those suffering from economic displacement. The commission recently awarded 135 federal rental housing vouchers to very low-income tenants, which allow individuals to pay up to 30 percent of their income toward rent. That’s just a portion of the 1,500 federal vouchers the commission has committed to provide rental assistance to homeless individuals and families over the next three years.

Melinda Hohman, director of the school of social work at San Diego State University, said California’s high cost of living is a major contributor to homelessness.

“Housing is just very expensive in California, especially in Southern California,” Hohman said.

The percentage of the homeless population locally who lack shelters increased this year to 48 percent, from 47 percent last year. But it’s down from 58 percent in 2011.

The data shows that California accounted for 21 percent of the nation’s homeless population in 2015. Los Angeles city and county jumped to No. 1 for having the most chronically homeless people in the country, tallied at 12,356.

The government defines chronically homeless as someone who is disabled and has gone without housing for a year, or several times over three years. L.A.’s total is nearly four times larger than New York City’s chronically homeless population, which was the second largest in the country with 3,275 people.

Correction This story has been amended from its original, which listed 10 too few chronically homeless people in the San Diego area for 2015.

San Diego’s chronic homeless population jumped to 1,689 from 1,245 last year, the data shows, and has increased more than 73 percent since 2007. Diaz said data for chronic homelessness is not perfect, since it’s determined through self-reported surveys conducted one night of the year.

The questions designed to determine chronic homelessness have changed over the years as well, she said, which could help explain such a large increase.

Efforts to reduce and eventually prevent homelessness altogether are underway, Diaz said. Homeless individuals with severe mental health issues will be able to receive permanent housing through funding approved by the county Board of Supervisors in September.

The board allocated $10 million toward the creation of affordable housing throughout the region, part of a $145.5 million spending plan from California’s Mental Health Services Act, passed by California voters in 2004. The act provides housing, treatment and recovery programs from a 1 percent tax on income from millionaires.

Diaz said the county has placed emphasis on “rapid rehousing” programs in particular, which provide short term financial assistance with costs such as rent and security deposits. Others help individuals negotiate with landlords or find more affordable housing.

“It’s an intervention that provides fast assistance so that folks can either avoid becoming homeless or avoid touching the shelter system,” Diaz said.

Rapid rehousing programs are effective in reducing homelessness, Hohman said, especially when individuals are not required to “jump through all these hoops” to receive assistance. Housing programs that require individuals to be evaluated, join therapy groups or receive counseling for drug abuse before they’re offered housing assistance tend to be less effective, she said.

“The programs should really focus on finding housing first, getting you stabilized, and then, if you’re ready, help you access all these other programs available,” Hohman said. “Not the other way around.”

The increase in homelessness in the San Diego area runs counter to the national trend.

The HUD report found an 11 percent decrease in overall homelessness across the U.S. since 2010, which is when President Obama launched Opening Doors, an initiative to prevent and end homelessness nationwide. San Diego has seen a 4.3 percent increase during that same period.

Data shows homelessness among veterans dropped by 4 percent nationally since last year.

“We have made tremendous progress toward our ambitious goals,” said HUD secretary Julin Castro in statement issued Thursday. “But our work is far from finished.”

In comparison to national trends, San Diego saw a 5 percent increase in veteran homelessness between 2014 and 2015, with more than 1,300 homeless veterans counted in January. Nearly 50 percent of them were found in unsheltered locations.

The total ranks San Diego at third in the country behind New York City and Los Angeles for homeless veterans, a slot it’s held three out of the last four years.

The Regional Task Force has scheduled next year’s count on Jan. 29. Diaz said the organization is in need of volunteers and those interested can register at https://www.rtfhsd.org/