Year	% of revenue
1972	63.81987577639752
1973	68.83673469387756
1974	86.95256113797211
1975	80.62453897221539
1976	79.04731761354644
1977	76.35551096721237
1978	64.99712147380541
1979	73.97360292052794
1980	68.1958041958042
1981	62.855656697009096
1982	69.39554534336435
1983	65.04776538178903
1984	59.077221627408996
1985	51.38509295812666
1986	31.880824905810034
1987	41.21137304874164
1988	41.29141566265061
1989	51.47780678851175
1990	59.88061054858698
1991	51.16678596993558
1992	51.0198761811665
1993	74.72868217054264
1994	74.92569139312484
1995	66.16186361409291
1996	59.46269816851003
1997	46.50342973810608
1998	39.26419438593054
1999	51.363286800626895
2000	61.4168826977797
2001	57.19568202032465
2002	67.13482446850304
2003	64.95371034121965
2004	66.00168447939562
2005	68.02713843555239
2006	66.82516292784301
2007	66.56579460637805
2008	61.64433515042339
2009	52.314260495817024