divestiture of our arrow and moores businesses , and an unfavorable sales mix of international plumbing products , which , in aggregate , decreased sales by two percent . net sales for 2016 were positively affected by increased sales volume of plumbing products , paints and other coating products and builders' hardware . 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 . net sales for 2016 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 32.2 percent , 34.2 percent and 33.4 percent in 2018 , 2017 and 2016 , respectively . the 2018 gross profit margin was negatively impacted by an increase in commodity costs , the recognition of the inventory step up adjustment established as a part of the the acquisition of kichler , an increase in other expenses ( such as logistics costs and salaries ) and unfavorable sales mix . these negative impacts were partially offset by an increase in net selling prices , the benefits associated with cost savings initiatives , and increased sales volume . the 2017 gross profit margin was positively impacted by increased sales volume , a more favorable relationship between net selling prices and commodity costs , and cost savings initiatives . selling , general and administrative expenses as a percent of sales were 17.7 percent in 2018 compared with 18.6 percent in 2017 and 18.7 percent in 2016 . the decrease in selling , general and administrative expenses , as a percentage of sales , was driven by leverage of fixed expenses , due primarily to increased sales volume , and improved cost control . the following table reconciles reported operating profit to operating profit , as adjusted to exclude certain items , dollars in millions: .
what was the difference in operating profit margins as adjusted between 2016 and 2017?
operating profit margin in 2018 was negatively affected by an increase in commodity costs , the recognition of the inventory step up adjustment established as a part of the the acquisition of kichler and an increase in other expenses ( such as logistics costs , salaries and erp costs ) . these negative impacts were partially offset by increased net selling prices , benefits associated with cost savings initiatives and increased sales volume . operating profit margin in 2017 was positively impacted 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 . due to the recently-announced increase in tariffs on imported materials from china , and assuming tariffs rise to 25 percent in 2019 , we could be exposed to approximately $ 150 million of potential annual direct cost increases . we will work to mitigate the impact of these tariffs through a combination of price increases , supplier negotiations , supply chain repositioning and other internal productivity measures . other income ( expense ) , net other , net , for 2018 included $ 14 million of net periodic pension and post-retirement benefit cost and $ 8 million of realized foreign currency losses . these expenses were partially offset by $ 3 million of earnings related to equity method investments and $ 1 million related to distributions from private equity funds . other , net , for 2017 included $ 26 million related to periodic pension and post-retirement benefit costs , $ 13 million net loss related to the divestitures of moores and arrow and $ 2 million related to the impairment of a private equity fund , partially offset by $ 3 million related to distributions from private equity funds and $ 1 million of earnings related to equity method investments. .