Measuring the Impact of State Pro-Housing Policies: Empirical Traps to Avoid

Why It Matters

Accurate measurement of state pro‑housing policies is critical to ensure they effectively lower housing costs and bolster economic competitiveness, guiding evidence‑based reforms in a tightening affordability landscape.

Key Takeaways

• State governments increasingly adopt pro‑housing legislation across political spectrum.
• Policies often bundle multiple measures, complicating causal impact analysis.
• Housing laws vary in strength; effectiveness hinges on detailed provisions.
• Implementation delays and local compliance affect timing of measurable outcomes.
• Robust evaluation requires accounting for policy interactions, enforcement, and lag periods.

Summary

The webinar, led by Harvard’s Joint Center for Housing Studies and Arnold Ventures’ Jenny Schutz, examined how states are rapidly embracing pro‑housing policies and the methodological pitfalls that hinder accurate impact measurement. Over the past five to six years, more than half of U.S. states have enacted legislation aimed at expanding housing supply, ranging from legalizing accessory dwelling units to eliminating parking minimums, reflecting growing concerns about affordability and economic competitiveness. Schutz highlighted several empirical challenges: policies are rarely isolated, often arriving as bundled packages that can reinforce or counteract each other; the strength of each law exists on a continuum rather than a simple on/off switch; and implementation timelines are staggered, with lengthy compliance periods for local jurisdictions. These factors complicate the classic before‑and‑after evaluation framework and demand nuanced control groups and timing adjustments. Concrete examples underscored the complexity. Montana passed five to six concurrent bills covering middle‑housing legalization, commercial‑corridor apartments, parking reforms, and streamlined permitting. Oregon paired statewide middle‑housing legalization with rent control, potentially offsetting supply gains. California’s 200‑plus supply‑focused bills over five years have outpaced local code‑update capacities, while its decade‑long ADU rollout illustrates how weak initial provisions can be eroded by loopholes before achieving strong outcomes. Massachusetts’ MBTA‑oriented transit‑district law illustrates a multi‑year rollout with staggered local compliance deadlines. The discussion concluded that rigorous, data‑driven evaluation is essential for policymakers to discern which policy elements truly lower housing costs and expand supply. Researchers must design studies that capture policy bundles, variable enforcement, and lagged effects, thereby providing states with actionable evidence to refine housing strategies and improve affordability for households.

Original Description

Since 2020, more than half of US states have adopted laws to boost the production of smaller, lower-cost homes. The policies vary, but the most common versions require local governments to allow accessory dwelling units (ADUs) and small multifamily buildings in residential neighborhoods, permit larger apartment buildings in commercial corridors, and/or streamline lengthy development processes. While policymakers and advocates need to know whether these reforms are working, few rigorous evaluations have been done. Jenny Schuetz, Vice President of Infrastructure, Housing at Arnold Ventures, will discuss the empirical challenges in evaluating state pro-housing policies and strategies for generating more reliable analyses.

04-03-26