Vertical analysis (common-size) percentages for Palau Company's sales revenue, cost of goods sold, and expenses are as follows.

Vertical Analysis                2019                2018                2017

Sales revenue....................100.0%..........100.0%............100.0%

Cost of goods sold................60.5............62.9.............64.8

Expenses................................26.0............26.6.............27.5

Did Palau's net income as a percent of sales increase, decrease, or remain unchanged over the 3-year period? Provide numerical support for your answer.