Year	gross (GPI)
1971	0.909569978713989
1972	0.908749997615814
1973	0.907679975032806
1974	0.907019972801209
1975	0.909219980239868
1976	0.917169988155365
1977	0.925979971885681
1978	0.940670013427734
1979	0.948939979076386
1980	0.950820028781891
1981	0.96696001291275
1982	0.974730014801025
1983	0.9966099858284
1984	0.999499976634979
1985	0.99838000535965
1986	0.992169976234436
1987	0.983749985694885
1988	0.980080008506775
1989	0.980390012264252
1990	0.986180007457733
1991	0.987429976463318
1992	0.992839992046356
1993	1.00871002674103
1994	0.980809986591339
1995	1.01629996299744
1996	1.0160299539566
1997	1.02197003364563
1998	1.02289998531342
1999	1.0215699672699
2000	1.03004002571106
2001	1.02265000343323
2002	1.0025999546051
2003	0.994270026683807
2004	0.979680001735687
2005	0.965579986572266
2006	0.961239993572235
2007	0.956439971923828
2010	0.970340013504028
2011	0.980080008506775
2012	0.975189983844757
2013	0.973039984703064
2014	0.964680016040802
2015	0.959569990634918
2016	0.9653599858284
2017	0.971040010452271
2018	0.975350022315979
2019	0.976090013980865
2020	0.980000019073486