Year	gross (GPI)
1970	0.708230018615723
1971	0.712819993495941
1972	0.720459997653961
1973	0.727890014648438
1974	0.736930012702942
1975	0.738829970359802
1976	0.73879998922348
1977	0.750169992446899
1978	0.759930014610291
1979	0.761879980564117
1980	0.768850028514862
1981	0.77658998966217
1982	0.778039991855621
1983	0.76758998632431
1984	0.764280021190643
1985	0.778410017490387
1986	0.797280013561249
1987	0.810310006141663
1988	0.79679000377655
1989	0.819949984550476
1990	0.814840018749237
1991	0.822690010070801
1992	0.828769981861115
1993	0.829519987106323
1994	0.831110000610352
1995	0.830919981002808
1996	0.834800004959106
1997	0.83500999212265
1998	0.832669973373413
1999	0.839439988136292
2000	0.839380025863647
2001	0.843559980392456
2002	0.838429987430573
2003	0.845669984817505
2004	0.850660026073456
2005	0.859269976615906
2006	0.867690026760101
2007	0.872579991817474
2008	0.881860017776489
2009	0.890349984169006
2010	0.896780014038086
2011	0.897109985351563
2012	0.912029981613159
2013	0.920120000839233
2014	0.92510998249054
2015	0.9307000041008
2016	0.931400001049042
2017	0.935850024223328
2018	0.93885999917984
2019	0.939170002937317
2020	0.940919995307922