Calculate cullumbers net income as a percent of sales round

Question

Vertical analysis (common-size) percentages for Cullumber Company's sales revenue, cost of goods sold, and expenses are listed here.

Vertical Analysis -  2017     2016    2015

Sales revenue -      100%    100%  100%

Cost of goods sold  61.9      63.2      66.5

Expenses                  25.0       27.1      28.9

Calculate Cullumber's net income as a percent of sales. (Round answers to 1 decimal place, e.g. 5.2.)

Did Cullumber's net income as a percent of sales increase, decrease, or remain unchanged over the 3-year period?