Almost 7,500 people live on this city’s streets. Studio apartments are renting for $3,500 and up on Craigslist. Evictions are rampant. San Francisco is in a housing crisis, and it has been for years. But just how many apartments would need to be built to fix it? A new study claims to have the answer: 71,668 units of rental housing would need to be built by 2030 to keep pace with demand.

The study, commissioned by the National Multifamily Housing Council and the National Apartment Association, examined all 50 states, plus 50 major metropolitan areas. The organizations determined that across the U.S., 4.6 million apartments would need to be constructed in the next 13 years to manage a growing population.

While 71,668 rental apartments in total need to be built in this seven-by-seven city, construction could happen at an average rate of 5,119 per year to meet demand, says the report. That’s just about 100 per week.

Studying the need for rental apartments — as opposed to large single-family homes — was a choice made in response to the country’s changing population. As our nation ages, people over 65 lean more toward apartment living than staying in large homes. International immigration is another reason: Research shows that immigrants have a higher propensity to rent, and typically do so for a longer period of time. And the cultural delay of childbirth over the past few decades has also pushed couples into renting apartments for longer, before investing in a home.

“Nationally and here in San Francisco, we’re experiencing fundamental shifts in our housing dynamics, as more people are moving away from buying houses and choosing apartments instead,” says Janan New, the executive director of the San Francisco Apartment Association. “Population growth in the San Francisco metro area is occurring as a result of both migration into the area as well as natural population growth, fueling new rental households in the area.”

S.F. is building as fast as developers can get approval to do so, but is it the right kind of construction? Many of the units currently being built, such as the just-approved 300-unit One Oak high-rise, will be put on the market for sale, not rent, contradicting the cultural data collected above. And those 300 units took three years just to get approved, with another four years of construction expected. At this rate, the 100 units needed to be built per week is nothing but a pipe dream.