Year	% of revenue
1972	48.510230179028405
1973	46.14044079958989
1974	43.99881791700096
1975	42.51521716702773
1976	40.04106214070639
1977	43.92787696658997
1978	48.74474943831203
1979	50.860487463964354
1980	50.16637047680268
1981	49.137544802867424
1982	49.72430934491348
1983	50.03701812611682
1984	48.77705773817574
1985	47.682317085317116
1986	45.54379397716938
1987	48.35966395208151
1988	48.18505908855664
1989	49.812184830708915
1990	48.13602506430652
1991	47.73146626898879
1992	44.6679806973427
1993	43.261837312828774
1994	42.70461609301289
1995	32.009889470622454
1996	32.807638410564564
1997	35.54829176554874
1998	35.28079145363096
1999	36.16498446416604
2000	33.27396052607906
2001	33.69590538482215
2002	34.30407816776965
2003	36.03919065771997
2004	35.67590872910586
2005	35.51049618320611
2006	35.07185313369949
2007	33.9161969554278
2008	33.33604523451165
2009	36.13886076140675
2010	36.70565590761031
2011	37.61217059404734
2012	37.830837398267086
2013	38.441348936061246
2014	38.33253170645268
2015	37.86806324405688
2016	38.42338501447152
2017	38.517615593083946
2018	38.99845298802498
2019	38.73054240664272
2020	39.97538533669343
2021	38.18882879023189
2022	37.36671906130172