Year	gross (GPI)
1971	0.462370008230209
1972	0.482769995927811
1973	0.514800012111664
1974	0.54816997051239
1975	0.592850029468536
1976	0.632629990577698
1977	0.780900001525879
1978	0.818139970302582
1979	0.843089997768402
1980	0.907119989395142
1981	0.961170017719269
1982	0.992730021476746
1983	0.998820006847382
1984	1.0236599445343
1985	1.04853999614716
1986	1.12194001674652
1987	1.0939199924469
1988	1.17208003997803
1989	1.17131996154785
1990	1.17568004131317
1991	1.15280997753143
1992	1.1645200252533
1993	1.16995000839233
1994	1.17303001880646
1995	1.19848001003265
1996	1.21765005588531
1997	1.2459499835968
1998	1.25843000411987
1999	1.27972996234894
2000	1.31166005134583
2001	1.33480000495911
2002	1.34694004058838
2003	1.34927999973297
2004	1.34567999839783
2005	1.34516000747681
2006	1.35451996326447
2007	1.36712002754211
2008	1.38349997997284
2009	1.39055001735687
2010	1.3806699514389
2011	1.36731994152069
2012	1.36809003353119
2013	1.33554995059967
2014	1.31130003929138
2015	1.31596994400024
2016	1.32737994194031
2017	1.33156001567841
2018	1.32647001743317
2019	1.32823002338409
2020	1.33463001251221
2021	1.33692002296448