According to the latest Annual Builder Practices Survey (ABPS), one in four new single-family homes were built in established neighborhoods in 2020.

 
Infill lots are spaces left over after developments and cities have already been populated. Homes built on infill lots were 18.6 percent of new homes, while homes built after tearing down an existing building constituted 6.4 percent of new homes.

The lack of developable land will likely boost infill development and helps explain its relatively high market share. With the record high lot shortages reported by the September 2021 survey for NAHB/Wells Fargo Home Market Index (HMI), new homes built on infill lots.

Market share of homes built on infill lots varies geographically. A share of nearly 25 percent or more in New England, the Middle Atlantic and the Pacific but barely 12 percent in the Midwest. Regional differences are based on the differences in the market shares of teardowns that show age of housing stock, climate, developable land and lot shortages in the various regions.

63 percent of new single-family detached homes were built in new residential developments yet, 12.4 percent of new single-family detached homes built were not built in a residential development.
https://nahbnow.com/2021/12/25-of-new-single-family-homes-are-infills-or-teardowns/?_ga=2.68873622.666526263.1639008901-1095980197.1639008901