Year	% of revenue
1979	5.02092050209205
1980	5.43859649122807
1981	6.7669172932330826
1982	11.438474870017332
1983	13.151364764267989
1984	10.642201834862385
1985	16.68765743073048
1986	11.04319478402608
1987	10.185185185185185
1988	10.87219135056777
1990	18.48832901074472
1991	14.460259478523744
1992	16.744576291501858
1993	16.012644429910615
1994	15.162391665937145
1995	14.327402135231319
1996	14.688398849472675
1997	14.987364025931216
1998	14.501322545511124
1999	13.307522621888085
2000	12.704243191893601
2001	12.793296089385475
2002	12.492621015348288
2003	12.900274473924977
2004	13.234430082256168
2005	8.545402913999869
2006	8.999623241109308
2007	8.066678169004739
2008	8.598365299020799
2009	10.669649880263595
2010	9.77437823196257
2011	17.70623982095983
2014	37.513238495612754
2015	37.55579736552966
2016	39.33897753625448
2017	40.088431834005895
2018	40.360216725566694
2019	39.447763161892
2020	32.900172329287045
2021	42.27206224024703