common-size income statement:

Sep. 26, 2020

Sep. 28, 2019

Sep. 29, 2018

Net sales

100.00%

100.00%

100%

Cost of sales

61.77%

62.18%

61.66%

Gross margin

38.23%

37.82%

38.34%

Operating expenses:

Research and development

6.83%

6.23%

5.36%

Selling, general and administrative

7.25%

7.01%

6.29%

Total operating expenses

14.09%

13.25%

11.65%

Operating income

24.15%

24.57%

26.69%

Other income/(expense), net

0.29%

0.69%

0.75%

Income before provision for income taxes

24.44%

25.27%

27.44%

Provision for income taxes

5.71%

4.03%

5.03%

Net income

20.91%

21.24%

22.41%

Growth rates: D% (2020/2019) = (current - previous/ previous) *100

= (274,515- 260,174/260,174) *100 = 5.51%

Growth rates: D% (2019/2018) = (current - previous/ previous) *100

= (260,174 - 265,595/ 265,595) * 100 = (2.04) %

What's an analysis of the income statement including why trends have occurred?