Year	% of revenue
1972	13.793103448275861
1973	10.294117647058822
1974	11.578947368421053
1975	10.44776119402985
1976	8.823529411764707
1977	11.20331950207469
1978	11.180124223602485
1979	14.350797266514807
1980	6.983655274888559
1981	7.665903890160183
1982	5.710491367861885
1983	3.313049357674104
1984	3.4653465346534658
1985	4.253567508232711
1986	6.025025711347275
1987	5.374440832877418
1988	3.270005757052389
1989	5.179957169502844
1990	6.244096225998676
1991	7.651317325860349
1992	8.111784131448365
1993	6.791801763785248
1994	6.004568898518641
1995	3.9878173744734147
1996	3.8777941972276566
1997	3.870618747367453
1998	4.289058897965945
1999	4.3062374518379265
2000	4.054304112901236
2008	1.4867415144190979
2009	1.4736819223120392
2010	1.1006572042571054
2011	1.0794638159986896
2012	1.0507074117666233
2013	1.0560564247660067
2014	1.1478813126450222
2015	1.2840274568446417
2016	1.3019106209172258
2017	1.2269936186432864
2018	1.516547942371121
2019	1.4249279176438094
2020	1.3190312977137821
2021	1.5769812245324037
2022	1.6851314869576948