Year	gross (GPI)
1970	0.969280004501343
1971	0.969510018825531
1972	0.971610009670258
1973	0.981660008430481
1974	0.970849990844727
1975	0.982219994068146
1976	0.991029977798462
1977	0.986400008201599
1978	0.990610003471375
1979	0.990249991416931
1980	0.996159970760345
1981	1.00560998916626
1982	0.998989999294281
1983	1.00587999820709
1984	1.00458002090454
1985	1.00495994091034
1986	1.00699996948242
1987	1.00764000415802
1988	1.00434994697571
1989	1.00478005409241
1990	1.00530004501343
1991	1.00679004192352
1992	1.00817000865936
1993	1.00767004489899
1994	1.00048005580902
1995	0.999090015888214
1996	1.00097000598907
1997	0.999180018901825
1998	0.997730016708374
1999	0.998910009860992
2000	0.99796998500824
2001	0.999719977378845
2002	0.997030019760132
2003	0.997669994831085
2004	0.998939990997314
2005	0.997940003871918
2006	0.996379971504211
2007	0.997630000114441
2008	0.997380018234253
2009	0.993390023708344
2010	0.992529988288879
2011	0.991659998893738
2012	0.99168998003006
2013	0.99524998664856
2014	0.995880007743835
2015	0.995779991149902
2016	0.996739983558655
2017	0.992990016937256
2018	0.995019972324371
2019	0.997009992599487
2020	0.999379992485046