Table 2.
Hierarchical models examining geographical associations with the soda:milk price ratio, soda price and milk price, nested within county and state (n 1743), USA
| Soda:milk price ratio | Soda price | Milk price | ||||
|---|---|---|---|---|---|---|
| Fixed effects | Estimate* | 95 % CI | Estimate | 95 % CI | Estimate | 95 % CI |
| Intercept | 0·3690 | 0·318, 0·420 | 0·2365 | 0·228, 0·245 | 0·6434 | 0·585, 0·702 |
| Region | ||||||
| Northeast | 0·0272 | −0·037, 0·091 | −0·0174 | −0·0276, −0·0072 | −0·0794 | −0·154, −0·0050 |
| Midwest | 0·0716 | 0·0086, 0·135 | −0·0127 | −0·0227, −0·0026 | −0·0994 | −0·173, −0·0264 |
| South | −0·0264 | −0·085, 0·032 | −0·0101 | −0·0195, −0·0008 | 0·0196 | −0·0486, 0·0878 |
| West | Ref. | Ref. | Ref. | |||
| Urbanicity | ||||||
| Large metropolitan (population ≥1 million) | Ref. | Ref. | Ref. | |||
| Small metropolitan (population <1 million) | 0·0298 | 0·0187, 0·041 | 0·0042 | 0·0010, 0·0074 | −0·0274 | −0·0410, −0·0139 |
| Micropolitan (population 10 000–50 000) | 0·0499 | 0·0315, 0·068 | 0·0095 | 0·0039, 0·0151 | −0·0361 | −0·0590, −0·0131 |
| Non-core areas (population <10 000) | 0·0655 | 0·0377, 0·093 | 0·0179 | 0·0092, 0·0266 | −0·0395 | −0·0745, −0·0045 |
| Additional control variable | ||||||
| TP price | −0·0059 | −0·0090, −0·0028 | 0·0049 | 0·0038, 0·0059 | 0·0187 | 0·0147, 0·0227 |
| Random effects | Variance | se | Variance | se | Variance | se |
| Between states | 0·00377 | 0·00095 | 0·000074 | 0·000025 | 0·00500 | 0·00128 |
| Between counties (in states) | 0·00092 | 0·00014 | 0·000062 | 0·000013 | 0·00119 | 0·00018 |
| Within counties | 0·00246 | 0·000094 | 0·000298 | 0·000011 | 0·00429 | 0·00016 |
| ICC (state level) | 0·527 | 0·171 | 0·477 | |||
| ICC (county level) | 0·129 | 0·231 | 0·115 | |||
ICC, intraclass correlation coefficient (the proportion of variation in price that is accounted for by differences at the state and county levels); TP, toilet paper; ref., referent category.
*
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; a negative coefficient indicates lower price of soda relative to milk; and positive coefficient indicates higher price of soda relative to milk. Soda and milk price are measured in 2011 US dollars.