Table 3.

The range in differences and mean differences in the average market basket price between Seattle (‘intervention’) and King County (‘control’), by food processing category, following Seattle’s minimum wage ordinance

	Baseline		Follow-up 1		Follow-up 2
Food processing category	Range in price differences ($US)†	Mean difference ($US)	Range in price differences ($US)†	Mean difference ($US)	Range in price differences ($US)†	Mean difference ($US)
Group 1: unprocessed or minimally processed foods	−1·77 to 6·73	1·97	−7·07 to 2·10	1·86	−2·74 to 10·56	4·88
Group 2: processed culinary ingredients	−1·71 to 2·10	−0·27	−0·01 to ·96	1·10	−1·34 to 0·49	−0·16
Group 3: processed foods	−0·81 to 3·38	1·48	−1·39 to 4·44	1·41	−1·73 to 0·00	−0·63
Group 4: ultra-processed foods	−4·09 to 4·23	−0·43	−2·64 to 4·96	1·41	−6·31 to 3·87	−0·47

Baseline, March 2015 (1-month pre-policy enactment); follow-up 1, May 2015 (1-month post-policy enactment); follow-up 2, May 2016 (1-year post-policy enactment).

^†Differences between prices were computed by subtracting the price of each food processing category (the sum of individual item prices within each category) in King County from the price of the same food processing category in the corresponding Seattle supermarket chain.