Year	% of revenue
1991	27.213332902393972
1992	29.92294538797318
1993	30.53659114410744
1994	30.873973925639785
1995	30.495065220703957
1996	30.126935504315988
1997	29.016923051170888
1998	29.471887208430154
1999	31.311544322421312
2000	30.26788533802486
2001	30.39747739823585
2002	32.00915110482851
2003	30.472373573127058
2004	30.541921765777737
2005	30.72361495444958
2006	29.924879029414562
2007	29.909215398178635
2008	31.039787103583645
2009	32.588472235563714
2010	31.449080196314515
2011	31.289574629168577
2012	30.997184580451844
2013	30.16383328900274
2014	29.91814986399712
2015	29.78401648840811
2016	29.55473783239851
2017	31.04831967898345
2018	30.250196491269122
2019	30.773827400200886
2020	31.946562144538788
2021	31.09055362214331
2022	30.0266649723412