Year	% gross
1973	100.623359680176
1974	100.301010131836
1975	99.8253173828125
1976	99.4283294677734
1977	98.8644714355469
1978	98.2699127197266
1979	98.4503326416016
1980	99.4787292480469
1981	98.8224716186523
1982	98.5473403930664
1983	99.344970703125
1984	100.59407043457
1985	99.8379135131836
1986	99.2146606445312
1987	97.6843338012695
1988	97.4354705810547
1989	96.1906585693359
1990	92.3543167114258
1991	93.5005111694336
1992	95.2474899291992
1993	95.8278579711914
1994	96.6254730224609
1995	98.4623565673828
1996	99.5036773681641
1999	101.027770996094
2000	98.2204437255859
2001	97.6406097412109
2002	97.0616989135742
2003	96.5818710327148
2004	96.4518280029297
2005	95.5045318603516
2006	95.3834075927734
2007	95.8412399291992
2008	95.4030075073242
2009	97.3412704467773
2010	97.6586303710938
2011	97.6346130371094
2012	98.5221862792969
2013	97.6897811889648
2014	97.2882995605469
2015	97.7587738037109
2016	97.1344833374023
2017	96.9318695068359
2018	96.4932327270508
2019	96.2709274291992
2020	96.3747634887695
2021	96.2489776611328