Michigan’s retail industry rang up its best sales performance in more than three years during June, based on a new survey released by the Michigan Retailers Association. The MRA’s “Michigan Retail Index” found 53% of retailers polled in June reported increased sales over the same month last year, creating a seasonally-adjusted performance index of 66.7. That was up significantly from 47.7 recorded both in May and June of 2013. Index values above 50 generally indicate positive activity; the higher the number, the stronger the activity. Meantime, 58% of retailers expect sales during the July-through-September period to increase over the same period last year, with a seasonally-adjusted outlook index at 69.5, down from 79.3 in both May and June of 2013.