Quantifying heterosexual cohabitation without a dedicated source. The example of Paris from the 19th century to the interwar period

Cohabitation had a history before it became widespread in the 1960s. While the characteristics of cohabiting couples can be examined through various sources, the historical quantification of the phenomenon is much more difficult to grasp in the absence of direct evidence. This article begins by examining the indirect measures of cohabitation that have been used in the literature. Then, using the case of Paris, these different methods are put into practice, in particular those based on birth statistics and nominal census lists. By comparing the results derived from these data series, this article highlights both their methodological limitations and their analytical value. It notably demonstrates that the use of birth data is particularly valuable for long-term analysis, as this data is often annual. This method is also advantageous for its time-saving benefits when statistical data is published. However, the data must be sufficiently detailed to be usable. Lastly, this method provides a good proxy for a certain type of cohabitation, namely fertile couples. Legitimations in marriage certificates also capture only a part of the phenomenon. As for the analysis of premarital cohabitation based on addresses in marriage certificates, it also only captures a portion of cohabitation. The article concludes by showing that, despite well-known and documented limitations, nominal census lists can, in some cases, be particularly useful for analyzing cohabitation outside of marriage. This is notably because they can be used to address cohabitation following widowhood or divorce, or even the cohabitation of people who are still married; in Paris between the two wars, these categories accounted for a full 40% of cases of cohabitation.