Year	gross (GPI)
1971	0.988640010356903
1972	0.991699993610382
1973	0.994480013847351
1974	0.99822998046875
1975	0.99397999048233
1976	0.992839992046356
1977	0.993749976158142
1978	0.992730021476746
1979	0.994080007076263
1980	0.99413001537323
1981	0.993900001049042
1982	0.992229998111725
1983	0.994000017642975
1984	0.994009971618652
1985	0.994419991970062
1986	0.981679975986481
1987	0.98580002784729
1988	0.985000014305115
1989	0.989719986915588
1990	0.996230006217957
1991	0.997749984264374
1992	0.994369983673096
1993	0.994989991188049
1994	0.994059979915619
1995	0.991079986095428
1996	0.992959976196289
1997	0.991559982299805
1998	0.991469979286194
1999	0.990920007228851
2000	0.989709973335266
2001	0.989740014076233
2002	0.99032998085022
2003	0.994180023670197
2004	1.00154995918274
2005	0.998470008373261
2006	0.991729974746704
2007	0.987659990787506
2008	0.983439981937408
2009	0.988889992237091
2010	0.987079977989197
2011	0.990520000457764
2012	0.99167001247406
2013	0.989049971103668
2014	0.993589997291565
2015	0.990970015525818
2016	0.994920015335083
2017	0.997269988059998
2018	0.994880020618439
2019	0.99330997467041
2020	0.994930028915405