Year	gross (GPI)
1971	0.595070004463196
1972	0.667909979820251
1973	0.700559973716736
1977	0.729560017585754
1978	0.859109997749329
1979	0.812269985675812
1980	0.845300018787384
1981	0.851629972457886
1982	0.857999980449677
1984	0.75041002035141
1985	0.785860002040863
1986	0.839129984378815
1988	0.809859991073608
1990	0.794290006160736
1991	0.791429996490479
1992	0.798229992389679
1993	0.794489979743958
1994	0.791849970817566
1995	0.806810021400452
1996	0.809010028839111
1997	0.81742000579834
1998	0.826380014419556
1999	0.844900012016296
2000	0.846400022506714
2001	0.851140022277832
2002	0.853510022163391
2003	0.858169972896576
2004	0.866580009460449
2005	0.868420004844666
2006	0.873250007629395
2007	0.88170999288559
2008	0.891240000724792
2009	0.903169989585876
2010	0.914420008659363
2011	0.927039921283722
2012	0.934065043926239
2013	0.940358936786652
2014	0.946547389030457
2015	0.954333245754242
2016	0.954895853996277
2017	0.9623002409935
2018	0.962274074554443
2019	0.965516924858093
2020	0.967871189117432
2021	0.972314178943634