An “impulse” purchase is distinguished from a “destination” purchase. If you get into your car to specifically go to the hardware store, everything you buy there is a “destination” purchase because it’s why you drove your car. However, if, on your way home, you see a convenience-store sign that says “All two-liters $1,” and you stop to buy some, that’s an impulse buy. You made the purchase on impulse, and the sign’s information compelled you to stop and make the purchase.
How important are impulse buys to various businesses? You probably never saw a sign for a dentist’s office and decided to drop in. But if you’re traveling, unless you already have a reservation to lodge and/or eat, virtually every “stop” would be an impulse buy. You wouldn’t know to stop unless a sign informed you about available goods and/or services.
The Institute of Traffic Engineers estimates the following to represent impulse buys as a percentage of overall sales for various retail categories:
Impulse Buys of Overall Sales
For a discussion about how a court case highlighted the effects of signs and impulse buys, see the entry in this section entitled "What happened in the Denny's v. Agoura Hills Pole-sign case?".