At last count there were 6,400 homeless people living in San Francisco. But where does that figure come from, and is it reliable?

That's of particular importance since the number determines the amount of funding the city receives from the federal government for housing and services (we got $23 million in 2013). And those are some of the questions in the Examiner's coverage of the upcoming homeless census count planned for January 29th.

Here's how it works: Once every other year on a night in late January, hundreds of volunteers fan out over San Francisco with pens, clipboards, and flashlights to literally count the number of homeless people they see. In 2013 the count began at 8 p.m., this year it's 7 p.m. to 11 p.m.. This is a biennial practice all over the country required by the U.S. Department of Housing and Urban Development, and it's referred to as a "Point-in-Time" count.

Paul Boden, who became homeless himself at the age of 16 and is now the executive director of homeless advocacy nonprofit Western Regional Advocacy Project, told the Examiner that he finds the number deceptive. He and others criticize the black-and-white federal homelessness definition, which excludes people who might find shelter some nights in an SRO hotel or with friends and family though they lack a permanent residence.

Homeless people, according to federal law, live in shelters or places "not designed or ordinarily used for regular sleeping accommodation for human beings," including in vehicles, camping in parks, or squatting in abandoned buildings. However, city law has a broader homelessness definition, and would include those staying temporarily in SROs

Here's the entire 2013 report. There, you'll see breakdowns showing the number of single homeless people versus homeless people in families, and stats about the disproportionate number of black and latino homeless people. By way of example, in 2013 24 percent of homeless people were black, thought only 6 percent of the overall SF population was.

One particularly crucial figure debunking the "magnet theory" of how homeless people tend to flow into San Francisco from elsewhere is also in there: About 61 percent of our homeless population was already living and working in San Francisco when they became homeless. Therefore it's thought to be likely some were priced out of or evicted from their homes. Helping to address the inbound homeless issue, SF has a program called Homeward Bound that buys bus tickets for people with family members willing to take them in elsewhere, a program that has relocated 8,000 homeless in the last 10 years.

Nevertheless, the homeless count in our city has remained intractably unchanged over the last decade, hovering between 6,200 and 6,400 individuals year over year since 2005 despite every effort to house or relocate the homeless population. It remains true that, like Hawaii and parts of Southern California, SF is a particularly attractive place, climate-wise, to exist on the street, encouraging transients who land here to stay a while. But each time the homeless census happens politicians, and current Mayor's Office "homeless czar" Bevan Dufty, pray that the numbers move downward in order to prove that city money spent addressing the problem are being well used. Hopes may not be high for this count slipping downward partly because of how unseasonably warm this January is.

If you want to do your part to help establish this all-important census count, you can register to help with the count here.

Previously: City's Homeless Census Finds A Shift In Demographics
Mayor's Report Says 19,000 Homeless Off SF Streets, But 8,000 Were Just Bused Out Of Town
As Shelters Dwindle, The City Focuses On Street Medicine For Homeless