A jump in Hartford’s retail vacancy rate can be blamed largely on recent closings of mom-and-pop stores, according to a new study by industry tracker KeyPoint Partners.

Small business vacancies spiked over the last year to 100,000 square feet, more than twice that of any other submarket in the Greater Hartford region. As a result, the vacancy rate in Hartford increased to 18.5 percent from 15 percent, according to KeyPoint.

Further underscoring the fact that small stores are the greatest concern for retail space in Greater Hartford, the region’s vacancy rates increased in just three store size categories – the ones smaller than 10,000 square feet. The highest vacancy rate, 18.9 percent, was recorded by the smallest tenants, those less than 2,500 square feet, up from 17 percent the year before. Of the 96 new vacancies in the city, only eight are more than 5,000 square feet, emphasizing the fact that smaller independent retailers are struggling to maintain viability, particularly in urban markets where unemployment runs high and discretionary dollars are at a premium, KeyPoint reported.

Tenants smaller than 2,500 square feet represent nearly one-fifth of the retail inventory in Greater Hartford, the largest segment in the region. The other small store categories experiencing vacancy rate increases were the 2,500- to 4,999-square-foot segment, which jumped to 14.5 percent from 12.8 percent, and the 5,000- to 9,999-square-foot category, which increased to 14.9 percent from 14.2 percent.

Overall, the retail vacancy rate in Greater Hartford increased to 12 percent from 11.8 percent. Total retail space in Greater Hartford included 37.4 million square feet at the end of the 2012 study period, a "nominal" decrease from the 37.5 million square feet reported last year, according to the report. Some spaces converted to non-retail uses, contributing to the negligible decline in inventory this year. New retail construction moved at a snail’s pace as developers remained on the sideline. Existing conditions in the market may be playing a large part in their decision.