Estimating the lagged effect of price discounting: a time-series study on sugar sweetened beverage

Mamiya et al. BMC Public Health (2022) 22:1502

https://doi.org/10.1186/s12889-022-13928-w

RESEARCH

Estimating the lagged efect of price

discounting: a time-series study on sugar

sweetened beverage purchasing

in a supermarket

Hiroshi Mamiya*

, Alexandra M. Schmidt, Erica E. M. Moodie and David L. Buckeridge

Abstract

Background: Price discount is an unregulated obesogenic environmental risk factor for the purchasing of unhealthy

food, including Sugar Sweetened Beverages (SSB). Sales of price discounted food items are known to increase during

the period of discounting. However, the presence and extent of the lagged efect of discounting, a sustained level

of sales after discounting ends, is previously unaccounted for. We investigated the presence of the lagged efect of

discounting on the sales of fve SSB categories, which are soda, fruit juice, sport and energy drink, sugar-sweetened

cofee and tea, and sugar-sweetened drinkable yogurt.

Methods: We ftted distributed lag models to weekly volume-standardized sales and percent discounting generated

by a supermarket in Montreal, Canada between January 2008 and December 2013, inclusive (n=311weeks).

Results: While the sales of SSB increased during the period of discounting, there was no evidence of a prominent

lagged efect of discounting in four of the fve SSB; the exception was sports and energy drinks, where a posterior

mean of 28,459 servings (95% credible interval: 2661 to 67,253) of excess sales can be attributed to the lagged efect

in the target store during the 6 years study period.

Conclusion: Our results indicate that studies that do not account for the lagged efect of promotions may not fully

capture the efect of price discounting for some food categories.

Keywords: Sugar sweetened beverages, Price discounting, Lagged efect

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Background

Sugar Sweetened Beverages (SSB) represent the largest

source of dietary sugar in many nations [1] and are epi￾demiologically linked to obesity, overweight and nutri￾tion-related chronic diseases [2]. Price discounting, the

temporary reduction of price per unit food, is one of the

most prevalent marketing tactics used by food retailers

and manufacturers to increase sales [3, 4]. Price discount￾ing is reported to have more consistent association with

increased sales than other in-store promotions (e.g., dis￾play, fyer, and giveaway promotions) and media advertis￾ing [5]. Prevalence of price discounting is often reported

to be disproportionately higher among highly processed

‘junk’ food including SSB [6], and people’s purchasing of

SSB appears to be particularly susceptible to price dis￾counting – more so than solid (non-beverage) food [7,

8]. Price discounting may lead to the overconsumption

of the promoted food items [3, 9, 10], thus being a retail

Open Access

*Correspondence: [email protected]

School of Global and Population Health, Department of Epidemiology,

Biostatistics, and Occupational Health, McGill University, Suite 1200, 2001

McGill College Avenue, Montreal, QC H3A1G1, Canada