Keep getting a shock at the checkout? You're trying too hard, say researchers

New research released by the Georgia Institute of Technology suggests that consumers keen to count their cents while shopping are normally doing more harm than good, as on average they will underestimate their basket price.

While 84.6 percent of shoppers "at least sometimes" keep track of how much they are spending, those that try to keep a running total in their head are a lot less accurate than those who estimate throughout their shop.

Koert van Ittersum, of the Georgia Tech College of Management, examined the behavior of shoppers in both high income and low income grocery stores. Those that rounded prices up or down, guessed an average price per product for the basket and multiplied it by the number of items, or combined fitting prices (e.g., €1.20 and €1.80 equals a round €3) were more accurate than those who tried to calculate the total sum down to the last penny.

"When shopping in a grocery store, the chaotic, information-rich environment can tax a shopper's ability to mentally calculate the total basket price," says van Ittersum. "Shoppers could help themselves by sticking to shopping lists and using calculators."

The study also found that shoppers on tight budget, who are most motivated to try to track every expense, were among the most likely to overspend at the end. This also has an impact on perceptions of the store, suggests the study, as shoppers paying more than they expected to hold the retailer responsible.