Year	gross (GPI)
1970	0.644289970397949
1971	0.644919991493225
1972	0.652530014514923
1973	0.657069981098175
1974	0.664969980716705
1975	0.666180014610291
1976	0.669860005378723
1977	0.678179979324341
1978	0.689949989318848
1979	0.693319976329803
1980	0.704209983348846
1981	0.711969971656799
1982	0.737900018692017
1983	0.742550015449524
1984	0.749580025672913
1985	0.744790017604828
1986	0.752269983291626
1987	0.766250014305115
1988	0.759779989719391
1989	0.765179991722107
1990	0.768809974193573
1991	0.776009976863861
1992	0.77947998046875
1993	0.780650019645691
1994	0.777629971504211
1995	0.773360013961792
1996	0.768779993057251
1997	0.774240016937256
1998	0.774940013885498
1999	0.791249990463257
2000	0.798959970474243
2001	0.803359985351563
2002	0.805710017681122
2003	0.816049993038177
2004	0.811710000038147
2005	0.832790017127991
2006	0.843119978904724
2007	0.848999977111816
2008	0.858210027217865
2009	0.868770003318787
2010	0.877579987049103
2011	0.886579990386963
2012	0.892899990081787
2013	0.899810016155243
2014	0.902490019798279
2015	0.912109971046448
2016	0.914550006389618
2017	0.916339993476868
2018	0.916400015354156
2019	0.919149994850159
2020	0.923500001430511