Table 1.
Soda and milk prices at large chain supermarkets by census neighbourhood sociodemographics and geographic region, USA
| Soda ($US)*,† | Milk ($US)*,† | Soda:milk price ratio†,‡ | |||||
|---|---|---|---|---|---|---|---|
| Number of stores | Mean | sd | Mean | sd | Mean | sd | |
| Overall (2004–2011) | 1743 | 0·23 | 0·02 | 0·63 | 0·11 | 0·379 | 0·082 |
| Neighbourhood SES tertile§ | |||||||
| Lowest tertile (least advantaged) | 581 | 0·23 | 0·02 | 0·60 | 0·11 | 0·392 | 0·094 |
| Middle tertile | 582 | 0·22 | 0·02 | 0·61 | 0·11 | 0·379 | 0·08 |
| Highest tertile (most advantaged) | 580 | 0·23 | 0·02 | 0·65 | 0·10 | 0·363 | 0·069 |
| Proportion black/Hispanic quintile | |||||||
| Lowest (0 to 6·8 % black or Hispanic) | 349 | 0·23 | 0·02 | 0·57 | 0·11 | 0·418 | 0·096 |
| Second (6·8 to 13·0 %) | 349 | 0·23 | 0·02 | 0·62 | 0·12 | 0·384 | 0·087 |
| Middle (13·0 to 22·6 %) | 347 | 0·23 | 0·02 | 0·62 | 0·11 | 0·380 | 0·077 |
| Fourth (22·6 to 41·8 %) | 350 | 0·23 | 0·02 | 0·65 | 0·09 | 0·355 | 0·057 |
| Highest (41·8 to 98·2 %) | 348 | 0·22 | 0·02 | 0·65 | 0·11 | 0·354 | 0·071 |
| Urban classification | |||||||
| Large metropolitan (population ≥1 million) | 1165 | 0·23 | 0·02 | 0·64 | 0·10 | 0·363 | 0·069 |
| Small metropolitan (population <1 million) | 484 | 0·23 | 0·02 | 0·59 | 0·12 | 0·406 | 0·095 |
| Micropolitan (population 10 000–50 000) | 71 | 0·23 | 0·02 | 0·57 | 0·11 | 0·429 | 0·102 |
| Non-core areas (population <10 000) | 23 | 0·24 | 0·03 | 0·60 | 0·09 | 0·419 | 0·108 |
| Region | |||||||
| Northeast | 379 | 0·22 | 0·02 | 0·57 | 0·10 | 0·403 | 0·083 |
| Midwest | 315 | 0·22 | 0·02 | 0·57 | 0·14 | 0·411 | 0·115 |
| South | 641 | 0·23 | 0·02 | 0·65 | 0·09 | 0·360 | 0·064 |
| West | 408 | 0·24 | 0·02 | 0·67 | 0·09 | 0·358 | 0·06 |
SES, socio-economic status.
Prices are per 12 fl. oz (~355 ml) serving of soda and milk; all prices are inflation adjusted and reported in 2011 US dollars.
Statistical testing for bivariate associations between soda and milk prices and the soda:milk price ratio with demographic characteristic was performed. Normal linear regression was used for neighbourhood SES (continuous Z-score) and proportion black/Hispanic (ordinal variable of quintiles), and ANOVA models were used for the urban classification and region. P values for all comparisons were <0·0001.
A ratio <1·0 indicates that the average price of a single serving of soda is less than the price of a serving of milk, while a ratio>1·0 indicates that a serving of milk is more expensive than a serving of soda on average. The ratio can be interpreted as the price of soda as a percentage compared with that of milk; for example, a ratio of 0·42 indicates that the price of a serving of soda is 42 % of the price of a serving of milk. A higher soda:milk price ratio indicates a smaller difference between the two products and may be due to higher soda prices and/or lower milk prices.
Neighbourhood SES was derived from the log of the median household income; the log of the median value of housing units; the percentage of households receiving interest, dividend or net rental income; the percentage of adults 25 years of age or older who had completed high school; the percentage of adults 25 years of age or older who had completed college; and the percentage of employed persons 16 years of age or older in executive, managerial or professional specialty occupations.