Year	gross (GPI)
1971	0.99031001329422
1972	0.991590023040771
1973	0.993939995765686
1974	1.00097000598907
1975	0.999369978904724
1976	1.00736999511719
1977	1.0081000328064
1978	1.0096800327301
1979	1.01031005382538
1980	1.0127899646759
1981	1.01164996623993
1982	0.998690009117126
1983	0.988330006599426
1984	0.987489998340607
1985	0.988709986209869
1986	0.989310026168823
1987	0.990209996700287
1988	0.991840004920959
1989	0.992799997329712
1990	1.00022995471954
1991	0.994369983673096
1992	0.992290019989014
1993	0.990029990673065
1994	0.990180015563965
1995	0.993640005588531
1996	0.993770003318787
1998	0.9964399933815
1999	1.00942003726959
2000	1.01057004928589
2005	0.984269976615906
2006	0.98581999540329
2007	0.985909998416901
2008	0.986320018768311
2009	0.987969994544983
2010	0.989539980888367
2011	0.992229998111725
2012	1.00367999076843
2013	1.00638997554779
2014	1.00856995582581
2015	1.00838994979858
2016	1.00818002223969
2017	1.00546002388
2018	1.00332999229431
2019	1.00151002407074
2020	1.00258994102478