Communities must conduct field interviews of unsheltered homeless people every two years to be eligible for federal homeless funds.
The U.S. Department of Housing and Urban Development requires cities and counties to submit homeless population counts annually for consideration in awarding grants.
Government agencies aren't the only entities that can receive federal homeless dollars. Sacramento Steps Forward, a private nonprofit, is responsible for conducting local homeless counts and competing for HUD grants after taking over some of the county's homeless services to save costs in 2011.
Sacramento Steps Forward received $14.9 million in HUD grants last year, according to department data.
The graphic shows changes of homeless populations over time using count data from the California organizations that reported their numbers to HUD between 2005 and 2012.
Click the regions to see a population chart and the amount of HUD money each region received in 2011, the most recent year data is available.
Some organizations did not report all years. San Diego's homeless population numbers doubled after the city and county began reporting totals together.
The executive director of Sacramento Steps Forward said he expects the group's 2013 homeless count report to be available in May.