A computer system and computer-implemented method for controlling inventory of vendors at one level of a part distribution chain. The system includes a computer programmed with software for generating order data in response to reference data indicative of sales, inventory, demographics, and/or market characteristics of or pertaining to at least two vendors at the same distribution level. The order data is indicative of one or more of a recommended inventory increase transaction (such as a reorder by a vendor of a sold part); an inventory reduction transaction (such as a return of one or more parts in stock at the vendor); and a recommended stocking level of one or more parts by the vendor. When the computer is operated by personnel of a first vendor, it receives reference data concerning at least one other vendor at the same distribution level (in addition to processing reference data concerning the first vendor. When the computer is a host computer, it receives reference data from two or more vendors at the same distribution level. Preferably, the computer which generates the order data is programmed to generate the order data by processing forecast data which is generated by processing the reference data. To generate the forecast data, the computer preferably implements a point-of-sale based method or an actuarial method to determine a forecast of sales of a part by a vendor in a selected time period.