The U.S. faces a severe housing crunch. The country needs 3.8 million homes to house its citizens, according to estimates from Up For Growth, a research organization focused on housing affordability and production. That’s double from 2012, when the nation was 1.65 million units short. (Here is how much land people live on in every state.)

One potential solution is high-density housing. Buildings of five or more units can shelter more people on scarce urban and suburban land. In recent years, more cities across the country appear to be taking that approach, some growing their high-density building considerably more than others, often in response to development and population growth. 

To determine the cities that are building the most new high density housing, 24/7 Wall St. reviewed data from the U.S. Census Bureau’s monthly Build Permits Survey, using annual data from 2021 and 2016. Cities were ranked based on the percentage-point change in the number of new construction permits for buildings with five units or more as a share of all buildings from 2016 to 2021. All other data came from the Census.

Ranking by the change in high-density building permits, the Philadelphia-Camden-Wilmington metro area straddling New Jersey, Pennsylvania, Delaware, and Maryland could see a boom in multifamily construction if all are built. In 2021, 70% of new permits were for units of five or more units, up 34 points from 2016. Those units will help house the area’s 6 million residents. 

Not far behind is the Santa Rosa-Petaluma, California metro area north of San Francisco. More than 50% of new permits were for multifamily buildings in 2021, a 24 point increase from 2016. Between 2016 and 2021, permits for five or more housing units skyrocketed 430%. Its current population stands at a bit less than 500,000. But considering its location at the fringe of the tech industry in northern California, that number will likely grow. (Find out if any of these cities are also among the cities with the strongest economies in 2022.)

No. 3 is Worcester, in central Massachusetts, which recorded a 21.1-point jump in new permits for dwellings of five or more units as a percentage of all permits from 2016 to 2021. About 37% of new permits were for multifamily construction. Meanwhile, 53% of permits in No. 50 Denver were registered last year for buildings of five or more units, but that was a mere 2.3 percentage points higher than in 2016. In 20 cities, there was a 10 point jump in new permits for housing of five or more units.

Click here to see cities where new apartment construction is skyrocketing.

Click here to see our detailed methodology.