Behavioral Spillovers from Promoting Healthier Consumer Choices

2019-05-01

2019-08-31

Our raw data show clear evidence of a direct response among treated shoppers during the intervention period. While shoppers in both the treatment and control groups purchase the healthier varieties at a rate of about 22~percent before the intervention period, treated shoppers become 19~percent more likely to purchase these alternatives during the intervention period.
Since treated shoppers during the intervention period only received Swap And Be Healthy (SABH) information when they add specific goods to their baskets, this information does not reach shoppers in roughly 90~percent of purchase categories on average. Thus, receiving SABH information on healthier alternatives tripled the demand for healthier products among shoppers receiving the nudge.

About one-third of this response comes in the form of shoppers switching to directly adding healthier varieties to their shopping baskets, creating a spillover effect on shopping behavior after the completion of the intervention. In particular, we find a persistent change in consumption decisions after the intervention with a magnitude of about 80~percent of the direct effect on adding healthier varieties.

We then use the recently developed causal forest method to examine how the intervention impacts various types of shoppers differently.
We use this method to characterize shoppers in the top and bottom quartiles of the distribution of responsiveness to the intervention. The shoppers most responsive to the intervention tend to exhibit a distinct profile. First, those who shop more often and purchase more products encounter a higher intensity of treatment and respond more to the intervention. Second, more-responsive shoppers exhibit less-healthy tendencies while also demonstrating some degree of nutritional awareness: they purchase more junk foods and are more likely to add junk foods just before checking out; but they are more likely to shop for produce before adding junk to their basket, and they have higher baseline demand for the healthier varieties of the experimental products. Third, they make decisions more quickly, allocating less time to evaluate each product, selecting fewer on-sale items, and making fewer changes in the supermarket they check out from.

A unique aspect of our dataset is that it allows us to examine the impact of the SABH intervention on behavior across other dimensions of the shopping trip. While the intervention promoted specific healthier alternatives, it also had effects on purchasing behaviors that extend beyond the immediate scope of the intervention. Shoppers who were more responsive to the intervention exhibited modest but discernible shifts toward other healthier purchasing behaviors: they purchase more-expensive products, with more fiber, lower levels of cholesterol, and buy less junk food. In contrast, shoppers who were less likely to have a direct response to the intervention also adjusted their behavior along other dimensions in response to the intervention: they purchased cheaper products, changed supermarkets more often, spent more time shopping, and purchased more junk food and products with higher levels of saturated fat.

In collaboration with a registered dietitian, we identified 78~food items in 15 categories of staple foods (e.g., milk, pretzels, pudding, and soup) that had healthier alternatives in terms of having less sugar, less saturated fat, less sodium, lower glycemic index, more fiber, and added iodine. We selected healthier alternatives that closely resembled the unhealthy target items in both characteristics and price.
For example, instead of suggesting brown rice as a healthier alternative to jasmine rice, we recommended a variety of white rice with a lower glycemic index (basmati rice). On average, the suggested healthier alternatives cost 2~NIS more than their counterparts, yet in about one-third of the categories, the healthier option was actually cheaper.

We randomly assigned 14,282 shoppers to either the treatment or control groups. Those in the treatment group encountered the SABH prompt every time they added one of the 78~designated less-healthy varieties to their basket (in contrast to the ``Swap and Save'' feature which only appears if a shopper presses a button). The prompt showcases a list of healthier alternatives, detailing their prices and reasons for being healthier (e.g., reduced fat, no added sugars), allowing shoppers to effortlessly switch to a healthier choice with a simple click.

The intervention lasted for four months (May - August 2019). For each shopper in our sample, we collect data on any shopping basket created on the platform in the six months preceding the intervention and the three months after the intervention ended.

Randomization done in office by a computer.

Individual

No

8,400 shoppers

8,400 shoppers making about 2 trips per month

4,200 shoppers for treatment and control