Year	gross (GPI)
1971	0.988919973373413
1972	0.988619983196259
1973	1.01055002212524
1974	0.998910009860992
1975	0.996410012245178
1976	0.996640026569366
1977	0.993610024452209
1978	0.993589997291565
1979	0.999419987201691
1980	0.995500028133392
1981	0.996389985084534
1982	0.99779999256134
1983	1.00585997104645
1984	1.00947999954224
1985	1.01078999042511
1986	1.01014995574951
1987	1.01540994644165
1988	1.01728999614716
1989	1.0179500579834
1990	1.01820003986359
1991	1.02364003658295
1992	1.02016997337341
1993	0.997009992599487
1994	0.99466997385025
1995	0.993799984455109
1996	0.99439001083374
1999	0.992150008678436
2000	0.994490027427673
2001	0.993770003318787
2002	0.993160009384155
2003	0.991389989852905
2004	0.996460020542145
2005	0.995540022850037
2006	0.994220018386841
2007	0.996930003166199
2008	0.997669994831085
2009	0.996730029582977
2010	0.997659981250763
2011	0.99796998500824
2012	0.995859980583191
2013	1.00129997730255
2014	0.999710023403168
2015	0.998300015926361
2016	0.998860001564026
2017	1.00099003314972
2018	1.00478005409241
2019	1.01092004776001
2020	1.01420998573303