A retail store had sales of $45,900 in April and $56,200 in May. The store employs eight full-time workers who work a 40-hour week. In April the store also had eight part-time workers at 12 hours per week, and in May the store had nine part-timers at 17 hours per week (assume four weeks in each month).
Using sales dollars as the measure of output, what is the percentage change in productivity (dollars output per labor hour) from April to May? (Round your intermediate calculations and final answer to 2 decimal places.)