The federal Department of Housing and Urban Development (HUD) just submitted its report to Congress on what it calls “worst case needs” renters.

Generally, HUD defines the worst cases as renters who aren’t receiving government housing assistance, making less than 50 percent of the median income in their metro area, and paying more than 50 percent of that income toward rent.

It’s pretty easy for anybody making less than half of area median income to slide into such a trap, but it’s easier in some places than others.

Whereas only 31 percent of such renters in Boston and only 41 percent in Washington DC qualify as “worst case” under HUD, in San Francisco the figure is 49.5.

That’s not as bad as the likes of Los Angeles (54.5), Riverside (57.2), or Miami (60.9). But it still adds up to some 142,000 renters, about three percent of the total Bay Area population.

What’s the culprit? The 90-plus page HUD report cites a lot of factors, but one that pops up over and over: We are not building enough housing.

Here’s the reports highlights, in all of their grim detail:

HUD blames old-fashioned supply and demand. “This market-driven increase in worst case needs resulted from increased competition for a shrinking supply of affordable rental units. If the supply of rental units were unchanged, greater demand would increase competition for affordable units, drive up rents, and increase prevalence of worst case needs.”

“This market-driven increase in worst case needs resulted from increased competition for a shrinking supply of affordable rental units. If the supply of rental units were unchanged, greater demand would increase competition for affordable units, drive up rents, and increase prevalence of worst case needs.” Although, there’s room to argue that the problem was not the volume of construction but the amount of affordable housing. “For a growing population of very low-income renters, the expanding supply of rental units in 2015 failed to translate into increased availability of affordable housing. Unlike more expensive units, the stock of rental housing affordable to very low-income renters shrank between 2013 and 2015, and vacancy rates remained highest among the most expensive units.”

“For a growing population of very low-income renters, the expanding supply of rental units in 2015 failed to translate into increased availability of affordable housing. Unlike more expensive units, the stock of rental housing affordable to very low-income renters shrank between 2013 and 2015, and vacancy rates remained highest among the most expensive units.” Housing supply numbers are pretty grim. “For every 100 extremely low-income renters, only 66 affordable units existed, and only 38 of those units were affordable and available. If physically adequate units are required, then only 33 units were available for every 100 extremely low income renters.”

“For every 100 extremely low-income renters, only 66 affordable units existed, and only 38 of those units were affordable and available. If physically adequate units are required, then only 33 units were available for every 100 extremely low income renters.” And demand is only going up. “Between 2013 and 2015, both of the primary market forces of supply and demand contributed to increased worst case needs among the most vulnerable, extremely low-income subset—the supply of affordable and available units for these renters decreased modestly by 1.7 percent or 76,000 units, while an additional 127,000 households, a 1.1-percent increase, put upward pressure on demand for affordable units.”

“Between 2013 and 2015, both of the primary market forces of supply and demand contributed to increased worst case needs among the most vulnerable, extremely low-income subset—the supply of affordable and available units for these renters decreased modestly by 1.7 percent or 76,000 units, while an additional 127,000 households, a 1.1-percent increase, put upward pressure on demand for affordable units.” Rental assistance isn’t good enough to fill in the gap. “Even with one-fourth of very low-income renters receiving housing assistance, the private market’s supply of affordable rental housing is inadequate. Nationally, less than a third of very low-income renters were able to avoid severe housing problems in the unassisted private rental market in 2015. “

“Even with one-fourth of very low-income renters receiving housing assistance, the private market’s supply of affordable rental housing is inadequate. Nationally, less than a third of very low-income renters were able to avoid severe housing problems in the unassisted private rental market in 2015. “ Even when the economy is good, housing is on the rocks. “Substantial unmet needs for affordable rental housing remain even as incomes are improving. The unmet need for [...] housing continues to outpace the ability of federal, state, and local governments to supply.”

“Substantial unmet needs for affordable rental housing remain even as incomes are improving. The unmet need for [...] housing continues to outpace the ability of federal, state, and local governments to supply.” Nationwide, the number of renter in distress is almost at an all-time high. “Renter households with worst case needs increased to 8.3 million in 2015, up from 7.7 million in 2013 and slightly less than the record high of 8.5 million in 2011.”

“Renter households with worst case needs increased to 8.3 million in 2015, up from 7.7 million in 2013 and slightly less than the record high of 8.5 million in 2011.” Far more than housing conditions themselves, high rents is the number one problem facing renters. “Severely inadequate housing continues to be a relatively minor cause of worst case needs. In 2015, severely inadequate housing alone triggered a mere 1.8 percent of worst case needs, whereas 98.2 percent of worst case needs households had severe rent burdens.”

HUD makes the full congressional report available here.