Need help with the answer as well as the formula

Did Vallejo’s net income as a percent of sales increase, decrease, or remain unchanged over the 3-year period? Provide numerical support for your answer. (min 150 words)

Vertical Analysis

2012

Sales

100%

Cost of goods sold

60.3

Expenses

25.2

2011

Sales

100%

Cost of goods sold

64.6

Expenses

29.5

2010

Sales

100%

Cost of goods sold

66

Cost of goods sold

29.5