Restricting multi-buy price promotions on high fat, sugar or salt discretionary foods: analysis summary - briefing

4. Methods

SRUC and the University of Aberdeen analysed the changes in the purchase of HFSS discretionary foods if price promotions on these were restricted.

The analysis looked at changes in consumer behaviour such as switching within category or buying more non-discretionary foods as a result of restrictions to price promotions by estimating different demand elasticities^[5] for each category.

Using sales data which included if the product was subject to a price promotion, and data from experiments asking individuals to rank hypothetical alternative product choices, a model was constructed which isolates the price promotion aspect of demand for different products. This element could then in effect be switched on and off, allowing the amount spent by each representative household to be calculated before and after "restrictions were included". This provides an estimate of the difference in consumption of each food category.

The model assumes that the prices and promotions of other products remained the same and substitution was estimated using the inter category demand model (this measures the substitution between discretionary foods and non-discretionary foods). This provided an estimated change in quantities and nutrition simulating the restriction of promotions.

Further analysis was carried out to understand impact by: Household gross income, deprivation level using the Scottish Index of Multiple Deprivation (SIMD), Family Stage and Rurality.

Details of the methodology are set out in full in Section 3.1 of the SRUC-UoA report.