1. A computer system for generating and applying a formula for calculating an expected conversion rate, the computer system comprising: an electronic memory storage configured to store modules; a computer processor configured to execute the modules comprising at least: a data access module configured to access from a data repository stated metadata and derived metadata elements, wherein the stated metadata elements and the derived metadata elements are for a plurality of products that led to prior user conversions, a conversions module configured to determine the relevance of each stated metadata element and each derived metadata element in deriving expected conversion rates, wherein the determination is based on the use of a linear or logistic regression analysis, a formula generation module configured to generate on a periodic basis a formula based on the determination, wherein the formula takes into account a plurality of stated metadata elements and derived metadata elements that have been determined to be statistically relevant to expected conversion rates, and a formula application module configured to apply the formula to a plurality of products in an inventory database to assign a predicted conversion rate for each of the plurality of products in the inventory database.