Inclusionary zoning policies are an increasingly popular tool for addressing affordable housing challenges, with many cities and counties adopting such policies since 2000 (Thaden and Wang 2017). But the structure and features of these policies vary. Research suggests that the features of inclusionary zoning matter and need to be tailored to local market conditions (Ramakrishnan, Treskon, and Greene 2019; Schuetz, Meltzer, and Been 2008). Inclusionary zoning encourages or requires developers who are creating market-rate housing to set aside a percentage of the housing to be sold or rented at below-market rates. One common feature of inclusionary zoning policies is “in-lieu fees,” which developers can pay as an alternative to building onsite affordable units. (In-lieu fees are the most common name for this method of alternative compliance, but some jurisdictions might refer to this option as “buy-outs,” “opt-outs,” or “cash contributions.”) In-lieu fees are among the most hotly debated parts of inclusionary zoning, in part because little research exists on the variations in their structure and their advantages and disadvantages.