The Surprising Way You Can Be a Better Shopper

In the movie Forgetting Sarah Marshall, heartbroken Peter, played by Jason Segal, takes a surfing lesson in which he is repeatedly instructed to "do less." Of course, this makes no sense to the bewildered student as he futilely attempts to find the elusive balance between doing and not doing. 

It's a funny scene, and it turns out that the concept is more applicable than you might expect. In fact, there's a direct link between "doing less" and doing better -- maybe not at surfing, but certainly at grocery shopping. 

Motivated shoppers do more, but maybe they shouldn't
In a set of four field studies and complementary lab experiments, marketing professors Koert van Ittersum, Joost ME Pennings, and Brian Wansink examine the motivations and methods of grocery shoppers. They find that 85% of surveyed shoppers keep track of their spending "at least sometimes." Most shoppers -- about 57% -- use some form of estimation to figure out how much they're spending. 

Methods of estimating can range from adding the prices of each item in one's head -- e.g., $1.27 + $4.54 + $9.99 -- or by some version of rounding. "In deciding which strategy to use," write the authors, "our respondents seem to consider both accuracy and complexity." In other words, for most shoppers, tracking the cost of groceries tends to involve a trade-off between wanting to get the best estimate and not wanting to expend too much effort.

As you might imagine, more motivated shoppers, or those who really care about coming in under budget or making a good estimate of their expenditure, tend to value accuracy over simplicity. Does that make them better shoppers? 

Unfortunately, the researchers found that these motivated shoppers tended to do worse than less motivated shoppers. Their estimates were more biased and less accurate, and their confidence in their estimates was lower.

Why doing less is sometimes better 
The authors suggest that the mental costs of trying to be more exact reduce the accuracy of the motivated shoppers. With the prevalence of budgets in our shopping habits, this is an important finding: Sometimes, trying to be accurate can do more harm than good. Instead, grocery shopping presents you with an opportunity to do better by doing less. 

To give you an idea of how that might work, take the example of those shoppers in the study who were both motivated and experienced. Their performance improved when given financial reasons to be more accurate; but it wasn't because they were computational geniuses. Instead, they used the power of estimation to get the approximate cost of their shopping cart.

How to be a better shopper 
Of course, estimation implies rounding. Easy enough. But how you round is also part of the equation. 

For example, if you always round up or always round down, you'll be less accurate than if you adjust by rounding to the nearest whole number. Of course, the authors point out that many prices are in the $0.51 to $0.99 range, which would cause you to round up. It could make your estimate more inaccurate over time; but in the absence of better pricing, I'd argue that this isn't necessarily a bad thing. After all, you'll tend to overestimate your spending in this situation, which might be a nice surprise in the checkout line.

If you want to be more accurate than that without breaking your brain or the bank, I'd consider rounding to the nearest $0.50. This could give you the benefits of using approximate prices, but will be more accurate than rounding to the nearest whole, which, because of the way stores price their products, will introduce more error over time. 

Why should I care about this? 
It might seem like a lot of effort compared to just shopping mindlessly... and it is. But the fact is that most people shop on some kind of budget, or at least care about how much they're spending. Thus, making tweaks to improve that process could be quite broadly useful.  

But it also matters on an emotional level. We tend to view our satisfaction with a grocery shopping experience through the lens of how well we did from an estimation and budget perspective. When we pay more than we expected to, we tend to feel dissatisfied with the store. On the other hand, when we pay less, we feel better about ourselves.

That means that improving your ability to estimate the cost of your groceries, and stay within budget, could not only make your shopping experience more pleasant, but it could give you a little boost at the same time. And why wouldn't you want that?  

To learn more, take a look at Trying Harder and Doing Worse: How Grocery Shoppers Track In-Store Spending, by Koert van Ittersum, Joost ME Pennings, and Brian Wansink.