Year	gross (GPI)
1970	0.708339989185333
1971	0.712939977645874
1972	0.720560014247894
1973	0.727999985218048
1974	0.737039983272552
1975	0.73895001411438
1976	0.738889992237091
1977	0.75025999546051
1978	0.760010004043579
1979	0.761950016021729
1980	0.768920004367828
1981	0.776660025119781
1982	0.77810001373291
1983	0.767650008201599
1984	0.764339983463287
1985	0.778460025787354
1986	0.797330021858215
1987	0.810350000858307
1988	0.796829998493195
1989	0.819980025291443
1990	0.814869999885559
1991	0.822719991207123
1992	0.828800022602081
1993	0.82955002784729
1994	0.831139981746674
1995	0.830950021743774
1996	0.834839999675751
1997	0.835039973258972
1998	0.832690000534058
1999	0.839470028877258
2000	0.839410006999969
2001	0.843580007553101
2002	0.838450014591217
2003	0.845690011978149
2004	0.850679993629456
2005	0.85929000377655
2006	0.867709994316101
2007	0.872590005397797
2008	0.881869971752167
2009	0.890359997749329
2010	0.896790027618408
2011	0.897119998931885
2012	0.912029981613159
2013	0.920130014419556
2014	0.925119996070862
2015	0.930710017681122
2016	0.931410014629364
2017	0.935850024223328
2018	0.938870012760162
2019	0.939180016517639
2020	0.940919995307922