Year	gross (GPI)
1971	0.580399990081787
1972	0.608500003814697
1973	0.635060012340546
1974	0.654190003871918
1975	0.660380005836487
1976	0.673030018806458
1977	0.688069999217987
1978	0.702269971370697
1979	0.718640029430389
1980	0.756470024585724
1981	0.776530027389526
1982	0.802770018577576
1983	0.820280015468597
1984	0.841989994049072
1985	0.861069977283478
1986	0.879050016403198
1987	0.895449995994568
1988	0.899420022964478
1989	0.901880025863647
1990	0.903970003128052
1991	0.905260026454926
1992	0.905939996242523
1993	0.911539971828461
1994	0.912710011005402
1995	0.913309991359711
1996	0.912429988384247
1997	0.914889991283417
1998	0.925530016422272
1999	0.918569982051849
2000	0.925130009651184
2001	0.934660017490387
2002	0.940169990062714
2003	0.956539988517761
2004	0.962539970874786
2005	0.971379995346069
2006	0.972959995269775
2007	0.97298002243042
2008	0.972949981689453
2009	0.969900012016296
2010	0.965409994125366
2011	0.967079997062683
2012	0.963620007038116
2013	0.965550005435944