> The United States is short 4 million housing units, with a particular dearth of starter homes, moderately priced apartments in low-rises, and family-friendly dwellings

The number cited links to here:

https://upforgrowth.org/apply-the-vision/2023-housing-underp...

Which has this as the report:

https://upforgrowth.org/wp-content/uploads/2023/10/2023_Hous...

The number is driven by this definition:

> Missing Households. Households that may not have formed due to lack of availability and affordability, e.g. households with children over 18 years of age still living with their parents or individuals or couples living together as roommates at levels exceeding historical norms.