Year	% of revenue
1990	20.343919334439505
1991	18.18824337149896
1992	12.498796495394588
1993	9.511740530760893
1994	8.182069749526951
1995	8.765556054641054
1996	9.68477142297955
1997	13.2426142394694
1998	11.839751997138428
1999	11.283963340145782
2000	11.991580830905463
2001	11.492182394323654
2002	9.09147053828299
2003	7.221561901216917
2004	5.848366984501162
2005	6.759138381201045
2006	7.667361393373865
2007	8.080070502329095
2008	7.973155495525916
2009	8.674688135893126
2010	8.525103480815837
2011	7.933282846007499
2012	11.534732801772748
2013	12.789122733902897
2014	12.74148274533546
2015	13.463207921957535
2016	11.813964014937197
2017	11.52965576684803
2018	12.38195043767723
2019	14.357195362573025
2020	17.688400745493603
2022	16.01525689925959