The Longitudinal Study of Families as a Method of Research

families over a period of years is that it affords the opportunity to obtain information which is dynamic. Thus it is a valuable method suitable for use in many fields. The growth and decline of the family as a biologic unit can be described. In the field of population, growth is depicted by the number of children born to a given union in relation to the date of marriage and the age of husband or wife. However, the size of the family is dynamic for reasons other than growth. It is subject to depletion over a period of time by death of members, and also to dissolution by divorce or separation from the family of one spouse. The growth of the family as a social unit can also be described if measurable characteristics of such growth can be developed. Also, the family can be described as an economic unit and since changes in this respect provide fairly objective data, it is possible to note them over a period of time. In the field of anthropology, Kluckhohn has suggested that contemporaneous observation of persons over a period of time may yield even better and more reliable information concerning culture and personality than is obtained from retrospective life histories (1). An adequate description of a population of families is more difficult than is a description of a population of persons. The family is complex and is constantly undergoing change. An extreme example of its complexity may be cited. The mobility among a sample of Negro tuberculous households in Upper Harlem, New York, was studied. This investigation included a description of the movement of persons into and out of the households. The households were composed of the immediate 'From the Milbank Memorial Fund. This paper was presented at the Annual Conference of The Milbank Memorial Fund, November 14-15, 1951.