Year	% of revenue
1972	5.2962988875673345
1973	4.706959706959712
1974	4.549823774431272
1975	4.594853062706747
1976	4.175393416424835
1977	3.9685555880376855
1978	3.765344664778092
1979	3.532723214392977
1980	3.1009169194728408
1981	3.5239372582021344
1982	3.4005712245626563
1983	3.617431053339045
1984	3.443036226128397
1985	3.2312475585246565
1986	2.4175412293853134
1987	2.564917955334268
1988	2.2448518218798377
1989	2.0061636197076513
1990	1.6164897422511018
1991	1.4887644577693515
1992	2.311257660123809
1993	2.0816831836305845
1994	3.1937982002126075
1995	2.0242261233223267
1996	1.987238200385355
1997	1.6577077813360523
1998	1.4987500400628184
1999	1.2209836205607874
2000	1.0709722616732986
2001	1.055422080082528
2002	1.0491239751664179
2003	1.102368546774134
2004	0.42437441529485076
2008	0.943334693871359
2009	0.8936083064323028
2010	0.9616323272815059
2011	1.0636477283917751
2012	1.0507074117666233
2013	0.989562495537925
2014	1.1027912453218298
2018	1.1623867835546804
2019	1.0882592188296076
2020	0.9457419855739462
2021	0.8820238452775516
2022	0.8918741565113664