Year	% of revenue
1973	27.296587926509186
1974	23.404255319148938
1975	25.507121277514027
1976	4.128843338213763
1977	5.149425287356322
1978	4.6590681863627275
1979	3.159820389156827
1980	2.763437594898269
1981	2.576298057867618
1982	2.950253055178373
1983	3.307223672758921
1984	3.843792214171681
1985	4.497805948317893
1986	6.004061944656004
1987	6.183973202782788
1988	9.056103666617583
1989	8.862166531932093
1990	17.495947125576755
1991	11.16590149067619
1992	16.082713989584914
1993	17.45589949975552
1994	21.15885621017609
1995	19.81842225726057
1996	16.863656323185012
1997	17.678275290215588
1998	17.607779522963497
1999	17.223872096334567
2000	19.46490137237235
2001	17.403743216803868
2002	16.318093472261495
2003	23.908053156768744
2004	23.638174189100628
2005	25.21872185900768
2012	7.563448333675686
2013	10.375827101521656
2014	10.024399837472131
2015	12.022588820397125
2016	13.873461994514741
2017	12.929877785731431
2018	10.852064556383276
2019	13.22820312241923