affected by lower sales volume of cabinets , the divestiture of our arrow and moores businesses , and an unfavorable sales mix of international plumbing products , which , in aggregate , decreased sales by approximately two percent compared to 2016 .
net sales for 2016 were positively affected by increased sales volume of plumbing products , paints and other coating products and builders' hardware , which , in aggregate , increased sales by approximately five percent compared to 2015 .
net sales for 2016 were also positively affected by favorable sales mix of cabinets and windows , and net selling price increases of north american windows and north american and international plumbing products , which , in aggregate , increased sales approximately one percent .
net sales for 2016 were negatively affected by lower sales volume of cabinets and lower net selling prices of paints and other coating products , which , in aggregate , decreased sales by approximately two percent .
net sales for 2015 were positively affected by increased sales volume of plumbing products , paints and other coating products , windows and builders' hardware .
net sales for 2015 were also positively affected by net selling price increases of plumbing products , cabinets and windows , as well as sales mix of north american cabinets and windows .
net sales for 2015 were negatively affected by lower sales volume of cabinets and lower net selling prices of paints and other coating products .
our gross profit margins were 34.2 percent , 33.4 percent and 31.5 percent in 2017 , 2016 and 2015 , respectively .
the 2017 and 2016 gross profit margins were positively impacted by increased sales volume , a more favorable relationship between net selling prices and commodity costs , and cost savings initiatives .
2016 gross profit margins were negatively impacted by an increase in warranty costs resulting from a change in our estimate of expected future warranty claim costs .
selling , general and administrative expenses as a percent of sales were 18.9 percent in 2017 compared with 19.1 percent in 2016 and 18.7 percent in 2015 .
selling , general and administrative expenses as a percent of sales in 2017 reflect increased sales and the effect of cost containment measures , partially offset by an increase in strategic growth investments , stock-based compensation , health insurance costs and trade show costs .
selling , general and administrative expenses as a percent of sales in 2016 reflect strategic growth investments , erp system implementation costs and higher insurance costs .
the following table reconciles reported operating profit to operating profit , as adjusted to exclude certain items , dollars in millions: .

2017
2016
2015
Operating profit, as reported
$1,169
$1,053
$914
Rationalization charges
4
22
18
Gain from sale of property and equipment
—
—
(5)
Operating profit, as adjusted
$1,173
$1,075
$927
Operating profit margins, as reported
15.3%
14.3%
12.8%
Operating profit margins, as adjusted
15.3%
14.6%
13.0%

operating profit margins in 2017 and 2016 were positively affected by increased sales volume , cost savings initiatives , and a more favorable relationship between net selling prices and commodity costs .
operating profit margin in 2017 was negatively impacted by an increase in strategic growth investments and certain other expenses , including stock-based compensation , health insurance costs , trade show costs and increased head count .
operating profit margin in 2016 was negatively impacted by an increase in warranty costs by a business in our windows and other specialty products segment and an increase in strategic growth investments , as well as erp system implementation costs and higher insurance costs .
.......................................................... .
.................................................................. .
..................................... .
........................................................ .
............................................ .
............................................. .

Question: Analyse this data from a financial earnings document. what was the percentage change in the gross profit margins from 2016 to 2017
Choices:
0.02395
23.9521
5.59441
0.8
0.45749
Correct choice index: 0