Year	% of revenue
1990	36.571068155678404
1991	40.892878140555794
1992	33.45808766982825
1993	29.654744355652106
1994	27.278104801477376
1995	31.76215363376393
1996	32.05105597981634
2004	28.452723208174003
2005	28.8169124619862
2006	32.48737552601398
2007	39.41200760708743
2008	32.812735921964546
2009	33.57964867313186
2010	28.710708182899065
2011	27.554791757096663
2012	27.343613050259464
2013	22.26183069662838
2014	21.651731286625537
2015	22.516180556240723
2016	27.080822471645032
2017	27.854670260029135
2018	24.587385215598974
2019	23.774471997288167
2020	22.507295976483306
2021	20.997145618989133