Year	gross (GPI)
1970	0.604189991950989
1971	0.603280007839203
1972	0.611540019512177
1973	0.620869994163513
1974	0.627319991588593
1975	0.640489995479584
1976	0.65394002199173
1977	0.668799996376038
1978	0.682770013809204
1979	0.710919976234436
1980	0.7257000207901
1981	0.739560008049011
1982	0.749400019645691
1983	0.759329974651337
1984	0.773159980773926
1985	0.786249995231628
1986	0.79926997423172
1987	0.808550000190735
1988	0.810920000076294
1989	0.826120018959045
1990	0.836149990558624
1991	0.840040028095245
1992	0.851170003414154
1993	0.85673999786377
1994	0.858160018920898
1995	0.866810023784637
1996	0.839619994163513
1997	0.867910027503967
1998	0.87458997964859
1999	0.882340013980865
2000	0.889900028705597
2001	0.898379981517792
2002	0.905369997024536
2003	0.910229980945587
2004	0.913590013980865
2005	0.914380013942719
2006	0.916620016098022
2007	0.922580003738403
2008	0.927259981632233
2009	0.929849982261658
2010	0.932020008563995
2011	0.927770018577576
2012	0.938970029354095
2013	0.949670016765594
2014	0.958360016345978
2015	0.961969971656799
2016	0.965669989585876
2017	0.964470028877258
2018	0.965550005435944
2019	0.967580020427704
2020	0.970220029354095