Year	% of revenue
1972	5.072057945041816
1973	1.6831801360869048
1974	1.6367609674877726
1975	1.7237023104348559
1976	1.667668630515811
1977	1.758939184105209
1978	1.6815849593648176
1979	1.9125548784483324
1980	2.2317368059098874
1981	2.6717711878139685
1982	3.5094791434777117
1983	4.785318847818848
1984	4.678103323974439
1985	4.552855885947695
1986	3.6270710236698505
1987	4.530181390718802
1988	3.208587575048236
1989	3.335296203429324
1990	3.753428703392413
1991	3.797488050189205
1992	3.8434809410683703
1993	3.890643163961052
1994	3.8992745000191933
1995	3.4575020586328677
1996	3.3865215736577254
1997	3.4233812508237476
1998	3.3266322873874663
1999	5.083907436848613
2000	5.473184451643482
2001	5.418638684767717
2002	4.0722196234245995
2003	4.049061622580168
2004	3.7142738895460927
2005	3.408187646283859
2006	3.3110731575455237
2007	2.970494807745497
2008	2.923098013096476
2009	3.0470382407328716
2010	3.0457900628415
2011	3.0170771647227883
2012	2.726492028784979
2013	2.432184266213391
2014	2.2247246300011354
2015	2.330548776166611
2016	2.272654795400968
2017	2.148754143691646
2018	2.1214623824487977
2019	1.956354691645274
2020	1.9962755652393245
2021	1.8175301048870478
2022	1.7888392177621621