Year	gross (GPI)
1970	0.618920028209686
1971	0.617470026016235
1972	0.623520016670227
1973	0.63085001707077
1974	0.638050019741058
1975	0.642700016498566
1976	0.65149998664856
1977	0.66237998008728
1978	0.671169996261597
1979	0.691779971122742
1980	0.703329980373383
1981	0.715489983558655
1982	0.7255499958992
1983	0.733430027961731
1984	0.740559995174408
1985	0.749610006809235
1986	0.758300006389618
1987	0.767709970474243
1988	0.771229982376099
1989	0.782559990882874
1990	0.793070018291473
1991	0.799600005149841
1992	0.813440024852753
1993	0.821080029010773
1994	0.824169993400574
1995	0.837750017642975
1996	0.822809994220734
1997	0.846029996871948
1998	0.857179999351501
1999	0.868420004844666
2000	0.877290010452271
2001	0.886300027370453
2002	0.895259976387024
2003	0.903349995613098
2004	0.90693998336792
2005	0.913670003414154
2006	0.917309999465942
2007	0.920419991016388
2008	0.923160016536713
2009	0.924130022525787
2010	0.926810026168823
2011	0.926519989967346
2012	0.933889985084534
2013	0.935810029506683
2014	0.940289974212646
2015	0.944939970970154
2016	0.942539989948273
2017	0.9444500207901
2018	0.948260009288788
2019	0.949790000915527
2020	0.953429996967316