Okay, exponential growth and decay is a simple understandable model but is it any good? It turns out the exponential decay is an excellent model for radioactive waste but neither decay or growth are particularly good ones for for population. Why not? One possible answer is that these models don't allow for anything like a stable population except for the unhappy one of extinction N=0. In this section you will redo the analysis for a slightly more useful model of growth called the logistic equation.