From exposure to composition: Market and household adjustments under Singapore's mandatory nutri-grade labeling policy.

Mandatory front-of-pack (FOP) labeling influences diets through consumer substitution, firm portfolio responses, and pricing. This study examined the market and household purchase implications of Singapore's Nutri-Grade (NG) policy - mandatory graded FOP label for pre-packaged beverages (A = most healthy to D = least healthy), analyzing market adjustments and household purchase composition around its implementation. Using representative household scanner data, we constructed a product-month panel to estimate difference-in-differences models of purchase volume and price for products classified as NG C/D versus A/B. We assessed supply-side responses using Poisson models of product entry/exit and decomposed market-level nutrient density changes into reformulation, entry/exit, and consumer switching. Finally, household fixed-effects interrupted time-series models evaluated nutrient density changes relative to counterfactual trends. Post-policy, the differential changes in purchase volume and price for NG C/D relative to A/B were statistically insignificant. However, new-product introductions shifted strongly toward NG A/B and product discontinuation rates did not differ between NG C/D and A/B. Decomposition indicated that market-level nutrient density improvements were driven predominantly by product entry and exit rather than consumer switching or reformulation. In contrast, household purchase-weighted sugar and energy density increased relative to counterfactual trends, while purchase-weighted Nutri-Score, a measure of the overall nutritional quality of beverages, improved. These findings highlight that mandatory graded labelling reshapes beverage markets primarily through firm portfolio adjustments rather than immediate consumer substitution. Notably, reductions in total sugar exposure at the household level need not coincide with improvements in the nutrient density of the household purchase basket, underscoring the importance of jointly tracking both exposure and composition metrics in evaluating the nutritional impact of FOP labelling policies.