• by Sarah Mahoney  @mahoney_sarah, September 11, 2007

You know those last-minute razors, bottled waters, magazines and M&Ms consumers grab when checking out at the store? Turns out that self-checkout systems dramatically reduce the purchase of these impulse items, according to a new study.

IHL Consulting Group reports that women purchase 32.1%--and men 16.7%--fewer impulse items when checking themselves out, primarily because those aisles typically contain far less merchandise.

The survey also turned up a number of strong cross-branding preferences. For example, when impulse buyers snag a Dr Pepper at checkout, they buy Altoids 71% more often than any other mint or gum, and Duracell batteries 43% more than any other battery brand. When they buy a Diet Dr Pepper, they buy M&Ms 42% more than any other candy. And those who buy Reese's Peanut Butter Cups turn to Doritos 39% more than any other salty snack.

The study also found that consumers are growing increasingly fond of self-checkout aisles, spending more than $137 billion in 2006--up 24% from the previous year. Self-checkout technology has become increasingly important, IHL says, handling anywhere from 20 to 50% of the daily transaction volume and 15 to 35% of the daily dollar volume in some retail stores.

While 91% of the shoppers surveyed say they have used or will use self-checkout aisles, 9% are refuseniks and are likely to say since they are paying full price, they are entitled to full service. (Some also worry about taking jobs away from people.)

Overall, 44% of respondents in the survey say they really like self-checkout. Southerners are among the most enthusiastic (some 75% have a positive view of the technology). And those earning more than $100,000 per year are 10% more likely to check themselves out than other income groups. The survey also found that the magic number for conversion was about six--of those who have used self-checkout at least six times, 86% say they like it.

The most common impulse buys are fattening. In fact, "the average American woman could lose 4.1 pounds a year simply from resisting the urge to purchase impulse items such as chocolate candies, chips and soda once [she is] in the checkout line," reports the study, which also finds that that women say they purchase and consume more than 14,300 calories per year at the checkout aisle.

And while women under 25 are the most prolific impulse buyers, men under the age of 25 are the heaviest consumers of caloric impulse items, "consuming enough calories each year for an additional 8 pounds."

Overall, women are more impulsive shoppers. On average, at a staffed checkout lane, women buy impulse items 24% more often than men. But at self-checkout lanes, women buy impulse items only 6% more often than men.