"The use of the logistic function in demographic techniques and analyses has increased significantly during recent years.  Nevertheless, not too much attention has been given to the function of the constants nor to the consequences of the implicit assumptions when the function is used for estimating some demographic parameters.  In this article, the author underlines the meaning of the constants in the logistic function when applied in some demographic cases, and gives some examples of the assumptions involved in the application of the logistic to the trends of urban/rural populations, life expectancies, and the logit transformation."  (summary in ENG)