Year	% of revenue
1972	28.57142857142857
1973	18.75
1974	9.72762645914397
1975	9.157212317666126
1976	11.021437578814627
1977	11.847862672500842
1978	11.756695415342715
1979	16.131204690409223
1980	16.64483037381875
1981	12.725482958041098
1982	8.503937007874015
1983	8.325564049972032
1984	8.375144731763799
1985	7.3200160879474465
1986	7.50823007010598
1987	7.356617197196147
1988	6.9738490150681285
1989	8.005014887948597
1990	8.384347396575007
1991	7.041690483929419
1992	7.0887366411224475
1993	6.648574652414394
1994	6.513489715926004
1995	6.090633766451271
1996	6.090990834422675
1997	6.128261693558283
1998	6.446046600334472
1999	6.817573257479034
2000	6.570225291881542
2001	6.634756170994057
2002	6.945915169596351
2003	6.8766365522166435
2004	6.44958927829717
2005	5.918587667492221
2006	5.234036189621654
2007	4.880867925626411
2008	5.605641756693851
2009	7.46363356760434
2010	6.2563256040602395
2011	5.896062270339179
2012	6.272498800201001
2013	6.828402982486562
2014	6.902174166236111
2015	6.71412850656962
2016	6.9340869574879935
2017	6.9157508305702695
2018	6.630686208240426
2019	7.043516892738558
2020	7.735973505998371
2021	4.864417506410274
2022	3.7675836131118112