Year	% of revenue
1990	25.37367567051637
1991	23.073322932917318
1992	25.29549747151648
1993	21.68482290537843
1994	20.798144238248696
1995	22.262246828789685
1997	24.026376188567887
1998	24.450902908606352
1999	26.344224062306097
2002	27.227344794257974
2003	30.040812463308647
2004	30.067740431373792
2005	30.78629103953524
2006	31.15305357612181
2007	31.862005309030632
2008	35.88160193204449
2009	32.63682990850679
2010	29.786675159020447
2011	30.69311580060739
2012	32.54777330363396
2013	30.278716661378734
2014	29.43879230634951
2015	30.322556536723127
2016	31.610461517716736
2017	32.889678986865306
2018	32.95357107138388
2019	32.94354385417999
2020	30.799343290798177
2021	30.08563945066619
2022	32.379092352982944