Year	gross (GPI)
1971	0.914600014686584
1972	0.918560028076172
1973	0.924030005931854
1974	0.929910004138947
1975	0.936779975891113
1976	0.941009998321533
1977	0.945729970932007
1978	0.954519987106323
1979	0.961839973926544
1980	0.971289992332459
1981	0.978799998760223
1982	0.985949993133545
1983	0.987919986248016
1984	0.989979982376099
1985	0.991389989852905
1986	0.991919994354248
1987	0.990970015525818
1988	0.992519974708557
1989	0.993120014667511
1990	1.00330996513367
1991	0.997439980506897
1992	0.998409986495972
1993	1.00911998748779
1994	1.01298999786377
1995	0.992780029773712
1996	0.996089994907379
1997	0.998179972171783
1998	0.992659986019135
1999	0.993610024452209
2000	0.976189970970154
2001	0.983319997787476
2002	0.970879971981049
2003	0.980289995670319
2004	0.993260025978088
2005	0.990549981594086
2006	0.988900005817413
2007	0.98896998167038
2008	0.989430010318756
2009	0.990819990634918
2010	0.989950001239777
2011	0.987070024013519
2012	0.989939987659454
2013	0.993749976158142
2014	0.994589984416962
2015	0.996529996395111
2016	1.00269997119904
2017	0.984040021896362
2018	0.978990018367767
2019	0.983399987220764
2020	0.990440011024475