Year	gross (GPI)
1971	0.97936999797821
1972	0.988380014896393
1973	0.992139995098114
1974	0.994430005550385
1975	1.00153994560242
1976	1.00104999542236
1977	1.0053299665451
1978	1.00202000141144
1979	1.00287997722626
1980	1.00104999542236
1981	1.00128996372223
1982	1.00168001651764
1983	1.00078999996185
1984	0.999719977378845
1985	1.00006997585297
1986	0.996710002422333
1987	0.998279988765717
1988	1.00057995319366
1989	0.999220013618469
1990	0.994530022144318
1991	0.993099987506866
1992	0.991460025310516
1994	0.985310018062592
1995	0.98565000295639
1996	0.983579993247986
1997	0.981109976768494
1998	0.982739984989166
1999	0.979749977588654
2000	0.981090009212494
2001	0.981549978256226
2002	0.982159972190857
2003	0.984510004520416
2004	0.984239995479584
2005	0.979589998722076
2006	0.982309997081757
2007	0.982219994068146
2008	0.986930012702942
2009	0.991490006446838
2010	0.993529975414276
2011	0.995310008525848
2012	0.994549989700317
2013	0.992240011692047
2014	0.993059992790222
2015	0.996800005435944
2016	0.99753999710083
2017	0.994189977645874
2018	0.992959976196289
2019	0.986580014228821
2020	0.979170024394989