Year	gross (GPI)
1971	0.935630023479462
1976	0.925040006637573
1981	0.925480008125305
1982	0.935090005397797
1983	0.930199980735779
1984	0.930419981479645
1985	0.946359992027283
1986	0.931739985942841
1987	0.926389992237091
1988	0.931770026683807
1989	0.944019973278046
1990	0.940590023994446
1991	0.946959972381592
1992	0.946590006351471
1993	0.9514399766922
1994	0.955340027809143
1995	0.955839991569519
1996	0.960539996623993
1997	0.965650022029877
1998	0.961279988288879
1999	0.966949999332428
2000	0.969690024852753
2001	0.969579994678497
2002	0.964429974555969
2003	0.96341997385025
2004	0.963039994239807
2005	0.966250002384186
2006	0.969860017299652
2007	0.968810021877289
2008	0.96560001373291
2009	0.965240001678467
2010	0.968720018863678
2011	0.970080018043518
2012	0.971570014953613
2013	0.972970008850098
2014	0.972320020198822
2015	0.97282999753952
2016	0.971989989280701
2017	0.97172999382019
2018	0.974089980125427
2019	0.980939984321594
2020	0.985939979553223