CRIS Scientific Seminar 2024-2025

Friday, December 6th 2024, 11:30 am
Sciences Po, Room K011 (1, St-Thomas)

Accessory Dwelling Units and California's Housing Affordability Crisis:
Evidence of Policy Success?

Nicholas J. Marantz

Associate Professor of Urban Planning and Public Policy
University of California, Irvine

Open seminar. Please register here to join us

Over the past two decades, housing affordability has become a pressing concern across many advanced economies.

While the United States does not exhibit a severe housing affordability problem on average, this national perspective masks significant regional disparities. California, in particular, stands out as the epicenter of housing unaffordability in the U.S., largely due to a chronic under-supply of housing.

This presentation assesses the causes and consequences of the recent boom in accessory dwelling units (ADUs) in California. ADUs—secondary units typically located in the yard or garage of single-family homes—have accounted for roughly a third all housing units permitted in California since 2018.

I analyze the factors driving the surge in ADU permitting, and I use regression models to identify the characteristics of neighborhoods where ADUs are most likely to be permitted. I conclude by discussing whether this trend represents a successful policy intervention that could inform housing strategies both in other parts of the U.S. and globally.

To find out more about Nicholas Marantz