Year	gross (GPI)
1978	0.954469978809357
1979	0.951409995555878
1980	0.974039971828461
1981	0.990899980068207
1982	0.996169984340668
1983	0.988179981708527
1984	0.992320001125336
1985	0.992470026016235
1986	1.002769947052
1987	1.00305998325348
1988	1.00794994831085
1989	1.00892996788025
1990	1.02226996421814
1991	1.01394999027252
1992	1.01756000518799
1993	1.02626001834869
1994	1.02824997901917
1995	1.02822995185852
1996	1.02670001983643
1998	1.03925001621246
1999	1.04993999004364
2000	1.04094994068146
2001	1.04735004901886
2002	1.04904997348785
2003	1.05518996715546
2004	1.04944002628326
2005	1.03778004646301
2006	1.0348299741745
2007	1.03194999694824
2008	1.02897000312805
2009	1.01971995830536
2010	1.00894999504089
2011	1.0166699886322
2012	1.01346004009247
2013	1.02708005905151
2014	1.04287004470825
2015	1.04752004146576
2016	1.02947998046875
2017	1.01091003417969
2018	0.999409973621368
2019	0.991479992866516
2020	0.992669999599457