Year	gross (GPI)
1973	0.769550025463104
1974	0.764859974384308
1975	0.840349972248077
1976	0.879710018634796
1977	0.885280013084412
1978	0.878480017185211
1979	0.869210004806519
1980	0.869279980659485
1981	0.864260017871857
1982	0.856700003147125
1983	0.858039975166321
1984	0.862969994544983
1985	0.866379976272583
1986	0.888469994068146
1987	0.898010015487671
1988	0.905569970607758
1989	0.914600014686584
1990	0.921230018138886
1991	0.933369994163513
1992	0.942560017108917
1993	0.943229973316193
1994	0.950179994106293
1995	0.95430999994278
1996	0.959919989109039
1997	0.967060029506683
1998	0.968609988689423
1999	0.974510014057159
2000	0.979189991950989
2001	0.984629988670349
2002	0.985549986362457
2003	0.987479984760284
2004	0.990840017795563
2005	0.987339973449707
2006	0.985279977321625
2007	0.982339978218079
2008	0.983910024166107
2009	0.982800006866455
2010	0.991760015487671
2011	0.993969976902008
2012	0.991209983825684
2013	0.994289994239807
2014	0.994379997253418
2015	0.992540001869202
2016	0.995350003242493
2017	0.996800005435944
2018	0.997889995574951
2019	0.998019993305206
2020	0.996930003166199