 Data from the Bank of America Institute finds the average monthly share of rent in total payments through May tops 9%. Of course, it varies from place to place. In Las Vegas, the average share of rent in May more than doubled the national average. The average monthly rent payment growth per small business client was up 12% year over year in May. And because that tracks business real estate rents in the producer price index, it suggests the increases are due to inflation rather than small businesses moving to bigger spaces.