San Francisco's biennial Point In Time Count of the city’s homeless population will happen Thursday, January 24, employing 500 volunteers to scour the city streets in the dead of night and manually count how many unsheltered residents they encounter.

The survey, which happens every odd-numbered year in January, is a seemingly strange ritual but a critical one for contextualizing the city’s ever-pressing homeless crisis.

Although the count is the subject of much criticism, the city has no choice but to conduct it—the federal government’s Department of Housing & Urban Development [HUD] demands it.

HUD says:

The Point-in-Time (PIT) count is a count of sheltered and unsheltered homeless persons on a single night in January. HUD requires that Continuums of Care [a federal anti-homelessness program] conduct an annual count of homeless persons who are sheltered in emergency shelter, transitional housing, and Safe Havens on a single night. CoCs also must conduct a count of unsheltered homeless persons every other year (odd numbered years). [...] Each count is planned, coordinated, and carried out locally.

According to San Francisco’s Department of Health & Human Services [HSH], “The Point in Time Count methodology has improved over the years and includes a visual assessment of people living unsheltered in San Francisco, a census of all shelter and transitional housing programs, and a survey of people experiencing homelessness.”

HSH says that on Thursday, “Volunteers will be asked to work in teams of two to three people and walk/drive all over assigned routes from approximately 8:00PM to midnight.”

This method can be highly subjective—in 2017, a reporter for the San Francisco Chronicle who volunteered to count recounted disagreements between team members about whether they could visually identify certain people as homeless or not.

Volunteers are trained not to directly ask anyone if they’re homeless and instead to employ their own judgment based on appearances. The count also includes a separate survey conducted by volunteers who are homeless themselves.

Despite criticism, the Point In Time Count naturally resists attempts to change or possibly improve methodology, since, as Department of Homeless Affairs Jeff Kositsky told Hoodline in 2016, that would harm its capacity to serve as an “apples to apples comparison” with past years.

Despite the iffy nature of the tally, the city has a lot of political capital invested in seeing the count go down, a goal that has proved increasingly elusive.

The most recent count in 2017 yielded a city homeless population estimate of 7,499—dow one percent from 2015 but up compared to years past, with factors like the cost of housing, joblessness, and substance abuse cited as the most likely contributors to homelessness in survey responses.

At the time, Homeless Affairs Director Kositsky predicted that the count would decrease significantly in 2019.

HSH will issue the results of Thursday’s count in a full report later this year.