This paper investigates the possibilities for the creation of a global dataset onfamily and household characteristics. This is done by scrutinizing and comparing twoprominent data sources on family system classifications. We first focus on historical data, bycomparing Emmanuel Todd’s classification of countries by family systems with ethnographicdata compiled in George Murdock’s Ethnographic atlas. Qualitative and quantitative testsshow that the two datasets frequently agree about family traits. Nonetheless, substantialdifferences exist that are mostly attributable to the focus of the datasets on different regions,and the difficulties in translating local, descriptive studies to hard data. We thereforeemphasize that it is important to know the strengths and weaknesses of the two datasets andemphasize that robustness checks are necessary in empirical research into familycharacteristics. We also compare these historical data with present-day data. This comparisonsuggests that family characteristics and the values associated with them can persist over longperiods.