Year	% of revenue
1972	4.6894409937888195
1973	3.938775510204082
1974	1.9830425338098243
1975	2.0408163265306123
1976	1.424275993036873
1977	1.7465456701171964
1978	0.535405872193437
1979	2.078067958438641
1980	2.4685314685314688
1981	1.0871261378413524
1982	0.6189082014601787
1983	0.3507248313180573
1984	0.2107869379014989
1985	0.32391942504302057
1986	0.2280388657545112
1987	0.1632685568652437
1988	0.17319277108433734
1989	0.08093994778067885
1990	0.04533776635937736
1991	0.03579098067287043
1992	0.024437927663734114
1993	0.06839945280437756
1994	0.06138537089687258
1995	0.015589506035365908
1996	0.019432254303434652
1997	0.12778895727148545
1998	0.7593200411502474
1999	5.42987364066156E-05
2000	5.520991001953479E-05
2001	7.095984479644235E-05
2002	0.7101683409549654
2003	0.7333806418843465
2004	0.6808921053758132
2005	0.6792981115351773
2006	0.7452941140134899
2007	0.8371134848942865
2008	0.7758607321417788
2009	0.5657283751630977