Year	% gross
1970	12.4886102676392
1971	12.9413204193115
1972	13.4081001281738
1973	13.0727100372314
1974	13.5965900421143
1975	14.337610244751
1976	14.8427801132202
1977	15.2394800186157
1978	15.5560398101807
1979	15.4370698928833
1980	15.6173601150513
1981	15.4803600311279
1982	15.7786703109741
1985	18.1023197174072
1986	19.3945198059082
1987	18.9795703887939
1988	19.7797603607178
1990	20.7651805877686
1994	20.5775203704834