Neighbourhood variation in the price of soda relative to milk and its association with neighbourhood socio-economic status and race

Objective: Soda consumption is high in the USA, especially among minorities and individuals of lower socio-economic status (SES); this may be due to its affordable price in relation to healthier alternatives. The objective of the present study was to examine geospatial variation in price of milk and soda, and the price of milk relative to soda, by neighbourhood SES and proportion of Hispanic and black individuals.

Design: Retailer soda and milk prices (n 2987; Information Resources, Inc. Academic Data Set 2004-2011) were linked to census block group sociodemographic characteristics (American Community Survey 2005-2009). Linear hierarchical regression models were used to adjust for confounders.

Setting: Large chain supermarkets and superstores (n 1743) in forty-one states and 1694 block groups (USA).

Results: For equivalent fluid ounces, price of soda on average was 62 % lower than milk ($US 0·23 v. $US 0·63 per serving) and there was high dispersion in milk price across geographic areas. After adjustment for confounding, neighbourhoods with a higher concentration of black and Hispanic individuals tended to have lower soda prices and higher milk prices (-$US 0·001 and +$US 0·007 in price per serving, respectively, for a one quintile increase in black/Hispanic population), while soda and milk both became less expensive as SES decreased (-$US 0·002 and -$US 0·015 in serving price per one sd decrease in SES index, respectively).

Conclusions: Neighbourhoods with a higher concentration of blacks and Hispanics may be at greater risk of higher soda consumption due to more affordable prices, in absolute terms and relative to the price of milk.