We should use demographically appropriate measures. To make big comparisons and analyze household and family composition across time and space, we must use the best available methodsandbesensitivetotheeffectsof variationinbothpopulationcomposition and the availability of kin. This means that we should avoid common measures currently in widespread use. Weshouldstudyspatialvariationinfamilies and households. Historical research on the demography of households and families has focused on analysis of small communities. One of the rationales for the community approach has been that localconditionshaveapowerfulinfluence on residence decisions. In fact, I argue, the only way we can evaluate the impact of local conditions on household and family structure is to conduct multilevel analyses that assess the characteristics of many communities simultaneously. We should study long-run historical change. Most historical studies of living arrangements focus on a single