Year	% of revenue
1990	20.141881312956368
1991	21.868589112066665
1992	24.176582869674696
1993	26.299769499005105
1994	25.07546251217137
1995	24.69922726103961
1996	25.062394191667973
1997	22.259865725275972
1998	23.631462768859862
1999	21.46125130727404
2000	25.21779439380662
2001	26.730100994307318
2002	26.9125586040474
2003	25.727874403838612
2004	21.655638271467453
2005	21.22605814538224
2006	22.57547223742822
2007	23.968155624950313
2008	22.68024906078949
2009	24.192265304063238
2010	22.798936196496495
2011	19.051240757335265
2012	21.42757953836711
2013	21.667464552937908
2014	22.78405983591465
2015	15.048393461608745
2016	15.189180737961225
2017	13.906477081565912
2018	10.943948521862495
2019	14.30370583110123
2020	19.710643530273064
2021	15.515785112077959