Year	% gross
1970	16.9910507202148
1972	18.1105709075928
1974	18.3179702758789
1979	20.3346195220947
1980	20.4717998504639
1981	20.1098804473877
1982	20.5428695678711
1986	24.5091495513916
1988	25.04075050354