Use of people counting systems in the retail environment is necessary to calculate the Conversion Rate, i.e. the percentage of a store's visitors that translate into purchases. This is a key performance indicator of a store's performance and is far superior to traditional methods, which only take into account sales data. Traffic counts and conversion rates together tell you how you got to your sales. i.e. if year-over-year sales are down: did fewer people visit my store, or did fewer people buy?