TRYSYS is a descendent of the BCTRY program, which was developed by Robert C. Tryon at Berkeley during the 1960s. See Cluster Analysis by Robert C. Tryon and Daniel E. Bailey (New York : McGraw-Hill, 1970). There are many other techniques available for performing dimension reduction, most of which lean heavily on orthogonal factor analysis. Tryon key-cluster factoring has the advantage of not forcing dimensions to be orthogonal, i.e., it allows a significant degree of correlation among dimensions (for example, in the case of the present analysis, between the "suburban" dimension and the "wealth" dimension). It is arguable that this capability allows its dimensions to approximate those of everyday experience--but perhaps not everyone would agree.