Year	gross (GPI)
1978	0.990620017051697
1979	0.990620017051697
1980	0.987900018692017
1981	0.996309995651245
1982	0.998860001564026
1983	0.994960010051727
1984	0.995429992675781
1985	0.998049974441528
1986	1.00083994865417
1987	1.00270998477936
1988	1.00595998764038
1989	1.00642001628876
1990	1.01412999629974
1991	1.00847995281219
1992	1.00922000408173
1993	1.01381003856659
1994	1.01496005058289
1995	1.0173100233078
1996	1.0132999420166
1998	1.02339005470276
1999	1.02909994125366
2000	1.02385997772217
2001	1.02711999416351
2002	1.02656996250153
2004	1.0244300365448
2005	1.01885998249054
2006	1.01806998252869
2007	1.01705002784729
2008	1.01811003684998
2009	1.01238000392914
2010	1.00574994087219
2011	1.00557994842529
2012	1.00244998931885
2013	1.00909996032715
2014	1.01689004898071
2015	1.01845002174377
2016	1.00967001914978
2017	1.00287997722626
2018	0.999819993972778
2019	0.995649993419647
2020	0.996890008449554