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Lot size, zoning, and household preferences

Urban density is a key feature of urban structure, and there is continuing interest in what determines density and how it might be influenced over time. Residential lot sizes are the underlying determinant of urban density, and lot sizes are determined by complex interactions of supply and demand forces. This article attempts to shed light on the extent to which lot size has been influenced by regulatory constraints, such as zoning rules or consumer preferences, drawing on data from the large metropolitan area surrounding Washington, DC. We find that new single-family development has been built on large lots, averaging in recent years between one half and one full acre, and that there is some evidence of convergence between inner and outer suburbs in lot sizes in new development over time. Our more detailed comparison of actual to allowable density using subdivision-level data reveals that developers only appear to be constrained by zoning rules in areas where regulations require that lots be larger than two acres. Finally, the hedonic analysis confirms that household preferences for larger lots are strong, but the value of additional acreage seems to be decreasing over time, in at least one inner suburban county.