Year	% of revenue
1973	27.42782152230971
1974	27.11528946066304
1975	19.723780750971084
1976	29.282576866764277
1977	28.804597701149426
1978	36.35272945410918
1979	39.996673873274574
1980	43.65320376556331
1981	43.75743162901308
1982	43.192198494013084
1983	42.782543826930244
1984	43.49748250030701
1985	43.661628473915165
1986	44.46560040619447
1987	43.66142746714764
1988	49.55087615962303
1989	46.31164106709782
1990	41.283202394313506
1991	40.599671257722605
1992	36.48313868244097
1993	35.92357167036522
1994	36.90636868702721
1995	42.41391587406541
1996	42.628439695550355
1997	43.46771887687997
1998	51.375406613967776
1999	50.942597941499535
2000	43.61061261569851
2001	50.72169515301413
2002	59.708923783990805
2003	55.6066544862085
2004	49.426093469398175
2005	41.80290262515039
2012	77.09472091808861
2013	72.63666449736425
2014	73.66194517454187
2015	67.85617165222892
2016	57.83275768769376
2017	63.07803614446086
2018	60.494553984062705
2019	58.4276612508871