Year	gross (GPI)
1970	0.991630017757416
1971	0.993839979171753
1972	0.998009979724884
1973	0.992380023002625
1974	0.987990021705627
1975	0.985830008983612
1976	0.998650014400482
1977	0.996050000190735
1978	1.00046002864838
1979	1.00019001960754
1980	1.00398004055023
1981	1.00707995891571
1982	0.99821001291275
1983	1.00260996818542
1984	1.00352001190186
1985	1.0025999546051
1986	0.995459973812103
1987	0.986710011959076
1988	0.992200016975403
1989	0.993659973144531
1990	1.00010001659393
1991	0.995000004768372
1992	0.987999975681305
1993	0.98114001750946
1994	0.985989987850189
1995	0.985289990901947
1996	0.987940013408661
1997	0.98760998249054
1998	0.985610008239746
1999	0.988569974899292
2000	0.985769987106323
2001	0.984170019626617
2002	0.988889992237091
2003	0.988030016422272
2004	0.987100005149841
2005	0.983399987220764
2006	0.984170019626617
2007	0.986689984798431
2008	0.984189987182617
2009	0.982119977474213
2010	0.979170024394989
2011	0.982569992542267
2012	0.985849976539612
2013	0.973450005054474
2014	0.977720022201538
2015	1.00476002693176
2016	0.982050001621246
2017	0.982919991016388
2018	0.974370002746582
2019	0.986400008201599
2020	0.990819990634918