Year	gross (GPI)
1970	0.970160007476807
1971	0.968299984931946
1972	0.959550023078918
1973	0.966530025005341
1974	0.970910012722015
1975	0.965810000896454
1976	0.965889990329742
1977	0.973420023918152
1978	0.972469985485077
1979	0.975009977817535
1980	0.979860007762909
1981	0.977729976177216
1982	0.9757000207901
1983	0.972540020942688
1984	0.972130000591278
1985	0.977199971675873
1986	0.979749977588654
1987	0.981509983539581
1988	0.987739980220795
1989	0.986989974975586
1990	0.989440023899078
1991	0.980920016765594
1992	0.980560004711151
1993	0.97664999961853
1994	0.972339987754822
1995	0.971560001373291
1996	0.970300018787384
1997	0.968859970569611
1998	0.966809988021851
1999	0.974929988384247
2000	0.970200002193451
2001	0.970489978790283
2002	0.969600021839142
2003	0.973219990730286
2004	0.973770022392273
2005	0.97027999162674
2006	0.972649991512299
2007	0.974030017852783
2008	0.969299972057343
2009	0.974510014057159
2010	0.968819975852966
2011	0.968379974365234
2012	0.975080013275146
2013	0.975480020046234
2014	0.975899994373322
2015	0.979510009288788
2016	0.980910003185272
2017	0.983780026435852
2018	0.985430002212524
2019	0.985580027103424
2020	0.982330024242401