Year	gross (GPI)
1973	0.797010004520416
1974	0.791450023651123
1975	0.856559991836548
1976	0.890590012073517
1977	0.896359980106354
1978	0.890359997749329
1979	0.882030010223389
1980	0.882730007171631
1981	0.878269970417023
1982	0.868089973926544
1983	0.864090025424957
1984	0.868920028209686
1985	0.872060000896454
1986	0.89749002456665
1987	0.90447998046875
1988	0.911899983882904
1989	0.918950021266937
1990	0.929669976234436
1991	0.934800028800964
1992	0.942929983139038
1993	0.945410013198853
1994	0.950070023536682
1995	0.957080006599426
1996	0.962589979171753
1997	0.966820001602173
1998	0.97079998254776
1999	0.974430024623871
2000	0.977270007133484
2001	0.982060015201569
2002	0.982760012149811
2003	0.985369980335236
2004	0.989279985427856
2005	0.986000001430511
2006	0.985310018062592
2007	0.983179986476898
2008	0.980069994926453
2009	0.982590019702911
2010	0.977789998054504
2011	0.979019999504089
2012	0.986280024051666
2013	0.99084997177124
2014	0.995140016078949
2015	0.994979977607727
2016	0.99931001663208
2017	1.00264000892639
2018	1.00415003299713
2019	1.00400996208191
2020	1.00112998485565