Year	% of revenue
1990	27.475009410682173
1991	34.986171473725804
1992	31.396826036982517
1993	26.163698844111217
1994	20.776018686737608
1995	25.20408543631416
1998	23.005647620925192
1999	18.186429345445323
2012	28.74105088948678
2013	27.04092230799266
2014	24.55280732959694
2015	20.57501942633197
2016	19.697634394087675
2017	19.3747415959037
2018	19.15662590161538
2019	20.64874847505758
2020	16.55026248123436
2021	18.486842961540777