Year	gross (GPI)
1973	0.525409996509552
1977	0.6735799908638
1978	0.676720023155212
1979	0.677670001983643
1981	0.708369970321655
1982	0.718640029430389
1983	0.70959997177124
1985	0.734650015830994
1986	0.742089986801147
1987	0.747370004653931
1990	0.727569997310638
1991	0.707080006599426
1992	0.71069997549057
1993	0.69964998960495
1994	0.685490012168884
1995	0.683640003204346
1999	0.725040018558502
2000	0.739080011844635
2001	0.755379974842072
2002	0.773599982261658
2004	0.812359988689423
2005	0.82217001914978
2006	0.837870001792908
2007	0.844319999217987
2008	0.8542600274086
2009	0.870639979839325
2010	0.876929998397827
2011	0.888090014457703
2012	0.89394998550415
2013	0.898970007896423
2014	0.904950022697449
2015	0.906029999256134
2016	0.917620539665222
2017	0.917689979076386
2018	0.931983292102814
2019	0.936689555644989
2020	0.938370943069458