Year	% of revenue
1990	22.15719445841525
1991	23.56351817671134
1992	29.641966189566986
1993	29.76512826684317
1994	22.16198014776931
1995	30.489972163471858
1996	28.116146369288902
1997	27.448393187878224
1998	25.815539473065492
1999	27.573959920421707
2000	29.13629956218746
2001	26.13363248699115
2002	27.690173807196157
2003	27.571382155736135
2004	26.44616183881257
2005	26.73116327628892
2006	23.516749073372665
2007	21.67649130658107
2008	20.452948190377448
2009	22.47205266254553
2010	22.235345743464755
2011	22.910552397244746
2012	22.125522275394495
2013	22.852652841318854
2014	23.382578460751525
2015	23.143380070577823
2016	23.97760333450561
2017	24.916666870461377
2018	24.847705592324978
2019	24.621584716376848
2020	27.287520191749316
2021	26.02068430555353
2022	22.545894469737227