People counting is used to measure the number and direction of people traversing a certain passage or entrance per time unit.
The resolution of the measurement is entirely dependent on the sophistication of the technology employed. The device is often used at the entrance of a building so that the total number of visitors can be recorded. Many different technologies are used in people counter devices, such as infrared beams, computer vision and thermal imaging.
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 makes purchases. This is the 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?