Year	gross (GPI)
1971	0.851220011711121
1972	0.860790014266968
1973	0.879710018634796
1974	0.903980016708374
1975	0.9305300116539
1976	0.931760013103485
1977	0.932820022106171
1978	0.937860012054443
1979	1.02662003040314
1980	0.989600002765656
1981	1.00053000450134
1982	1.00161004066467
1983	1.03835999965668
1984	1.03304994106293
1985	1.02198004722595
1986	1.03817999362946
1987	1.0382399559021
1988	1.04146003723145
1993	1.01978003978729
1996	1.04834997653961
1998	1.04656004905701
1999	1.03187000751495
2000	1.02192997932434
2001	1.02568995952606
2002	1.01148998737335
2003	1.02138996124268
2004	1.00643002986908
2005	1.01449000835419
2006	1.01912999153137
2007	1.01610004901886
2009	1.05478000640869
2010	1.04674994945526
2011	1.04764997959137
2012	1.05191004276276
2013	1.0456999540329
2014	1.04407000541687
2015	1.04126000404358
2016	1.03331005573273
2017	1.02814996242523
2018	1.02759003639221
2019	1.02665996551514
2020	1.02479004859924