  A first-order model for a stock market assigns to each stock a return
parameter and a variance parameter that depend only on the rank of the stock. A
second-order model assigns these parameters based on both the rank and the name
of the stock. First- and second-order models exhibit stability properties that
make them appropriate as a backdrop for the analysis of the idiosyncratic
behavior of individual stocks. Methods for the estimation of the parameters of
second-order models are developed in this paper.
