Year	gross (GPI)
1971	0.968020021915436
1972	0.973829984664917
1973	0.978359997272491
1974	0.98404997587204
1975	0.988990008831024
1976	0.992470026016235
1977	0.996949970722198
1978	0.99906998872757
1979	1.00329005718231
1980	1.00557005405426
1981	1.00577998161316
1982	1.00759994983673
1983	1.00732004642487
1984	1.00671994686127
1985	1.00760996341705
1986	1.00639998912811
1987	1.00504004955292
1988	1.00291001796722
1989	1.00279998779297
1990	1.00423002243042
1991	1.00523996353149
1992	1.00868999958038
1993	1.01254999637604
1994	1.01962995529175
1995	1.0289900302887
1996	1.03418004512787
1997	1.02845001220703
1998	1.03162002563477
1999	1.0263899564743
2000	1.01374995708466
2001	1.00548994541168
2002	1.0020899772644
2003	0.997749984264374
2004	0.995609998703003
2005	0.992699980735779
2006	0.9932000041008
2007	0.994279980659485
2008	0.997240006923676
2009	0.999409973621368
2010	1.00092005729675
2011	1.00240004062653
2012	1.00182998180389
2013	1.00088000297546
2014	0.998910009860992
2015	0.998470008373261
2016	0.998470008373261
2017	0.99753999710083
2018	0.99822998046875
2019	0.998579978942871
2020	0.998160004615784