table of contents other equity method investments infraservs .we hold indirect ownership interests in several german infraserv groups that own and develop industrial parks and provide on-site general and administrative support to tenants .our ownership interest in the equity investments in infraserv affiliates are as follows : as of december 31 , 2017 ( in percentages ) infraserv gmbh & co .gendorf kg ( 1 ) ................................................................................................... .39 .
[['', 'as of december 31 2017 ( in percentages )'], ['infraserv gmbh & co . gendorf kg ( 1 )', '39'], ['infraserv gmbh & co . hoechst kg', '32'], ['infraserv gmbh & co . knapsack kg ( 1 )', '27']]
infraserv gmbh & co .knapsack kg ( 1 ) ................................................................................................ .27 ______________________________ ( 1 ) see note 29 - subsequent events in the accompanying consolidated financial statements for further information .research and development our business models leverage innovation and conduct research and development activities to develop new , and optimize existing , production technologies , as well as to develop commercially viable new products and applications .research and development expense was $ 72 million , $ 78 million and $ 119 million for the years ended december 31 , 2017 , 2016 and 2015 , respectively .we consider the amounts spent during each of the last three fiscal years on research and development activities to be sufficient to execute our current strategic initiatives .intellectual property we attach importance to protecting our intellectual property , including safeguarding our confidential information and through our patents , trademarks and copyrights , in order to preserve our investment in research and development , manufacturing and marketing .patents may cover processes , equipment , products , intermediate products and product uses .we also seek to register trademarks as a means of protecting the brand names of our company and products .patents .in most industrial countries , patent protection exists for new substances and formulations , as well as for certain unique applications and production processes .however , we do business in regions of the world where intellectual property protection may be limited and difficult to enforce .confidential information .we maintain stringent information security policies and procedures wherever we do business .such information security policies and procedures include data encryption , controls over the disclosure and safekeeping of confidential information and trade secrets , as well as employee awareness training .trademarks .amcel ae , aoplus ae , ateva ae , avicor ae , celanese ae , celanex ae , celcon ae , celfx ae , celstran ae , celvolit ae , clarifoil ae , dur- o-set ae , ecomid ae , ecovae ae , forflex ae , forprene ae , frianyl ae , fortron ae , ghr ae , gumfit ae , gur ae , hostaform ae , laprene ae , metalx ae , mowilith ae , mt ae , nilamid ae , nivionplast ae , nutrinova ae , nylfor ae , pibiflex ae , pibifor ae , pibiter ae , polifor ae , resyn ae , riteflex ae , slidex ae , sofprene ae , sofpur ae , sunett ae , talcoprene ae , tecnoprene ae , thermx ae , tufcor ae , vantage ae , vectra ae , vinac ae , vinamul ae , vitaldose ae , zenite ae and certain other branded products and services named in this document are registered or reserved trademarks or service marks owned or licensed by celanese .the foregoing is not intended to be an exhaustive or comprehensive list of all registered or reserved trademarks and service marks owned or licensed by celanese .fortron ae is a registered trademark of fortron industries llc .hostaform ae is a registered trademark of hoechst gmbh .mowilith ae and nilamid ae are registered trademarks of celanese in most european countries .we monitor competitive developments and defend against infringements on our intellectual property rights .neither celanese nor any particular business segment is materially dependent upon any one patent , trademark , copyright or trade secret .environmental and other regulation matters pertaining to environmental and other regulations are discussed in item 1a .risk factors , as well as note 2 - summary of accounting policies , note 16 - environmental and note 24 - commitments and contingencies in the accompanying consolidated financial statements. .

Question: what is the percentage change in research and development expense from 2015 to 2016?
Answer: -34.5%