Year	% gross
1971	3.63989996910095
1972	4.4637598991394
1973	5.06548023223877
1974	5.54284000396729
1975	5.92340993881226
1976	6.63912010192871
1977	7.05039978027344
1978	8.5341100692749
1979	8.93653964996338
1980	10.4166698455811
1981	12.0379400253296
1982	14.2774696350098
1983	14.3493604660034
1985	14.7692499160767
1986	14.9846496582031
1987	12.7756595611572
1988	11.6631097793579
1989	11.3337202072144
1990	12.0012397766113
1991	12.0790004730225
1992	10.010479927063
2001	11.0858497619629
2002	11.144700050354
2009	12.2354898452759
2011	15.8301095962524
2012	15.5503301620483
2016	13.6688098907471
2017	15.42516040802