Trade Associations & Publications
Many trade associations compile industry data and make reports or other publications available to its members. Annual surveys generally feature statistics on member retailers by sales volume, square footage, trade area size, and store type.
The Monthly Mall Merchandise Index, maintained by the International Council of Shopping Centers (ICSC), reported sales per square foot in sporting goods stores and bicycle shops of $20 for July 2006. This information was obtained from the National Sporting Goods Association, a trade organization for retailers (and wholesalers) in the sporting goods industry.
Instead of shelling out big bucks for industry almanacs and association studies that you may only use once, take a trip to the local library and browse the Reference Desk. Many major business publications are made available for your retail research.
Review the annual reports of publicly traded companies for the data. Some businesses post their annual reports on website or just contact them for a copy. While you won't necessarily find their average sales per square foot detailed in the report, it may give enough clues to reach an estimate.
For example, if Acme Widgets reports it had $250K in sales last year and the store is around 8,000 square feet then we can roughly estimate the sales per square feet to be about $31.
U.S. Census Bureau
The United States Census Bureau data isn't just a count of households in your community. The Retail Trade Economic Data features sales by industry, annual survey results, as well as shopping centers retail sales per square foot by state.
Asking your local competitor how much in sales he's doing per square foot is probably useless. However, don't rule out asking a similar business in another city or even another state. That retailer may not feel threatened and may be willing to provide you the necessary information. Either way, it won't hurt to ask.
Once you learn the sales per square footage for your retail industry, don't be surprised if your business does more or less in sales. Factors such as location, competition, store layout, and level of inventory may greatly influence your store's sales results. The main goal is to generate more sales from existing space and constantly improve sales per square foot.