On Fisher’s Reproductive Value and Lotka’s Stable Population

Carlos Galindo, El Colegio de México

As Caswell (2001) states, Reproductive Value (RV) as presented in Fisher’s (1930) book is an obscure concept. Fortunately, Crow (2002) found the paper in which Fisher (1927) originally introduced RV, and he noted one important clarification: the assumption of ascribing the value of unity to newborns is not intended to be an absolute definition. Crow’s disclosure is of importance because it implies that RV, stable equivalent, and population momentum are only different faces of the same demographic tool. (I prove this statement in this paper). Furthermore, one letter from Lotka (1927) to Fisher’s editor explains that all points made in Fisher's paper were already present in his stable population theory. I revisit the original assumptions stated by Lotka, how they were present in Fisher’s work, and how can they help us to avoid confusions and misinterpretations of RV, stable equivalent, and population momentum.