Year	% gross
1972	6.48452997207642
1973	6.47635984420776
1974	6.89101982116699
1975	7.3585901260376
1976	7.82854986190796
1977	8.31488037109375
1978	8.90303993225098
1979	9.46543979644775
1980	10.1202297210693
1981	10.5648803710938
1982	11.0087099075317
1983	11.6216402053833
1984	12.2083301544189
1985	12.8190898895264
1986	13.4941701889038
1987	14.247540473938
1988	14.9633798599243
1989	14.3391199111938
1990	13.8965997695923
1991	13.4010496139526
1992	12.7729301452637
1993	12.2076597213745
1994	11.5290203094482
1995	11.0674200057983
1996	10.6854095458984
1997	10.1169996261597
1998	11.1600904464722
1999	10.9859800338745
2000	11.3187704086304
2001	11.3943901062012
2002	11.2468204498291
2003	11.2646398544312
2004	11.5285997390747
2005	12.1504697799683
2006	12.9240102767944
2007	13.4291000366211
2008	14.781439781189
2009	15.8331804275513
2010	16.1029891967773
2011	18.3391494750977
2012	20.5888004302979
2013	21.4058609008789
2014	22.151460647583
2015	23.1118793487549
2016	24.401439666748
2017	25.7670192718506
2018	25.8021392822266
2019	26.3884296417236
2020	27.4065799713135