Annual variations are often more brutal for nuptiality than they are for other demographic phenomena. Short-term economic movements, in particular, seem to have a more direct impact. In the long run, however, nuptiality is generally considered as a much more stable factor than, say, fertility which has undergone profound changes in all industrialized countries over the past hundred years. In this article the social scientists will attempt to study these recent trends in the light of longer-term ones, by comparing nuptiality movements in four countries: Canada, the United States, Australia and New Zealand. In this paper, they study the nuptiality of birth cohorts by calculating the proportion ever-married at age 50, and mean age at first marriage. Data are not always strictly comparable between one census and another, especially in Canada and the United States where geographical coverage has varied through time. However, the numbers involved were small. Moreover, the definition of marital status has not been changed, at least not the basic distinction between single and ever-married. Through a study of nuptiality trends for the single for about a hundred different birth cohorts, they will attempt to determine whether attitudes towards marriage have changed. But first, they must eliminate the structural effects which affect the phenomenon studied. For instance, marriage becomes more difficult for women and female nuptiality decreases when there is a scarcity of potential male partners.