Year	% of revenue
1972	1.6363551358174762
1973	1.3937853570550134
1974	1.2931345003962251
1975	1.4950450913829167
1976	2.006043850061081
1977	1.4758557539522232
1978	1.6683870657992654
1979	1.6024722688387703
1980	1.3922473803766395
1981	1.2879225996029948
1982	1.3614105304649717
1983	1.337782403722525
1984	1.614879162490255
1985	1.5616905679449111
1986	1.658425164323812
1987	1.68714690817964
1988	1.7214332464132478
1989	1.5890306244326597
1990	2.3308519807938737
1991	2.006000152349202
1992	2.1576887555246187
1993	1.9160066821468575
1994	2.0139221833097163
1995	1.6277301368346504
1996	1.4009788555105342
1997	1.276697442276479
1998	1.2338652586267356
1999	1.0697597515926343
2000	1.0359617567775998
2001	1.1412553961454859
2002	1.211359752521762
2003	1.1790262864269325
2004	1.1484631782649561
2005	1.168261518109774
2006	1.1503943755610564
2007	1.1737743583195095
2008	1.2355576022751273
2009	1.1701110695345722
2010	1.1878756121336238
2011	1.25192304188361
2012	1.2571487743615108
2013	1.2066887019831123
2014	1.2266466676139167
2015	1.2739514777862126
2016	1.2890408022340942
2017	1.2332861368817798
2018	1.5357915200319896
2019	1.6896734052163551
2020	1.3786659515017798
2021	1.566163886245923
2022	1.6472511004043002