Year	% of revenue
1988	16.833937614801528
1989	15.399686617570044
1990	14.564272576888495
1991	14.121000875311452
1992	13.72379713299786
1993	14.577756063274835
1994	12.221437515335747
1995	12.825701077003652
1996	12.439565682217012
1997	12.56150746193706
1998	12.57670229074711
1999	10.926448208228996
2000	11.114006333769739
2001	11.432970616943292
2002	10.747799867553896
2003	9.396854457233369
2004	9.297676232175203
2005	9.909812394166966
2006	9.476596062172575
2007	9.656488667940156
2008	9.39921542971739
2009	8.08970899392221
2010	8.812654236199908
2011	9.20229077583828
2012	9.74956956972167
2013	9.767765505130939
2014	9.83659006425225
2015	9.704967662989079
2016	11.035684925690914
2017	11.186012718152988
2018	11.062358320758278
2019	11.336830886900282
2020	8.833726830712783