Year	% of revenue
1973	5.9375
1974	4.085603112840467
1975	5.713128038897893
1976	6.327868852459016
1977	6.910131268933019
1978	7.354257181765125
1979	6.627579923147012
1980	5.246285507205976
1981	6.324597022271441
1982	7.6405104534346995
1983	12.304214059295171
1984	8.046167135321902
1985	7.273092907896501
1986	7.59135104393381
1987	7.47635778838254
1988	6.175276122518693
1989	6.422190879172543
1990	2.9273752410578697
1991	2.554704983505378
1992	2.7692582385144613
1993	4.2636526140795326
1994	4.325326860989628
1995	4.571638916414286
1996	4.413380382793196
1997	4.894346897760956
1998	4.185960218846941
1999	4.252575152542943
2000	2.1797846757776767
2001	3.2971479158171406
2002	3.3943824949432635
2003	3.2817004651303385
2004	3.261226172413498
2005	2.864037594462437
2006	2.9609690444145356
2007	2.460978947290987
2008	6.805209003567753
2009	1.5903455943819738
2010	7.63933346700652
2011	11.339485431945052
2012	11.167482161792917
2013	4.544546558002428
2014	3.2717097328262135
2015	3.6364343627145366
2016	-0.6943931586372579
2017	-4.874502353316641
2018	-1.4678347550928872
2019	2.8463155395125095
2020	2.7525391885156165
2021	1.7443341279976998
2022	3.240905240883273