Year	gross (GPI)
1970	0.984790027141571
1971	0.985520005226135
1972	0.987519979476929
1973	0.99115002155304
1974	0.989859998226166
1975	0.992030024528503
1976	0.991879999637604
1977	0.993780016899109
1978	0.993449985980988
1979	0.994000017642975
1980	0.994140028953552
1981	0.995829999446869
1982	0.998120009899139
1983	0.998629987239838
1984	0.997759997844696
1985	0.999019980430603
1986	1.00029003620148
1987	1.00803005695343
1988	1.00888001918793
1989	0.996580004692078
1990	0.994490027427673
1991	1.00153005123138
1992	1.01143002510071
1993	1.00399005413055
1994	1.00591003894806
1995	1.01066994667053
1996	1.0079300403595
1997	1.00197005271912
1998	1.00139999389648
1999	0.999960005283356
2000	0.997370004653931
2001	0.996169984340668
2002	0.994180023670197
2003	0.991209983825684
2004	1.00150001049042
2005	0.997510015964508
2006	0.995720028877258
2007	0.995220005512238
2008	0.995190024375916
2009	0.995989978313446
2010	0.993990004062653
2011	0.991680026054382
2012	0.992500007152557
2013	0.988510012626648
2014	0.989780008792877
2015	0.992179989814758
2016	0.992349982261658
2017	0.994120001792908
2018	0.992479979991913
2019	0.993189990520477
2020	0.993629992008209