Year	% of revenue
1972	6.896551724137931
1973	8.823529411764707
1974	5.263157894736842
1975	6.7164179104477615
1976	8.235294117647058
1977	5.394190871369295
1978	4.968944099378882
1979	4.555808656036446
1980	7.429420505200595
1981	8.352402745995423
1982	10.092961487383798
1983	7.6402974983096685
1984	6.134309083082221
1985	4.788693743139407
1986	4.93657867672266
1987	5.499951726579345
1988	10.300189160292787
1989	12.23432426831234
1990	10.5936879276098
1991	9.088593083243106
1992	11.136341369234582
1993	9.202450710695418
1994	12.859329737877111
1995	16.381077080724125
1996	16.357501144736293
1997	11.49917789708426
1998	10.114985659226496
1999	11.208298307565407
2000	10.474945103747748
2008	41.947170004088754
2009	33.63086257640697
2010	32.60363682394847
2011	36.170313854528246
2012	36.73949928908339
2013	33.755767838768385
2014	30.320634572350613
2015	21.25542558657084
2016	20.731991435583975
2017	24.11596650359251
2018	19.19116860102951
2019	19.08541618365707
2020	12.650851813253167
2021	14.416203946870548
2022	18.480430243555908