Year	gross (GPI)
1971	0.618399977684021
1972	0.619539976119995
1973	0.620620012283325
1974	0.624119997024536
1975	0.618470013141632
1976	0.630410015583038
1977	0.6387699842453
1978	0.644779980182648
1979	0.657130002975464
1980	0.662819981575012
1981	0.678839981555939
1982	0.691919982433319
1983	0.707350015640259
1984	0.725409984588623
1985	0.743600010871887
1986	0.761259973049164
1987	0.773899972438812
1988	0.763979971408844
1989	0.7985799908638
1990	0.81632000207901
1991	0.82344001531601
1992	0.855579972267151
1993	0.862829983234406
1994	0.851029992103577
1995	0.88577002286911
1996	0.811249971389771
1997	0.876820027828217
1999	0.923099994659424
2000	0.93283998966217
2001	0.941929996013641
2003	0.950519979000092
2004	0.957469999790192
2009	0.976069986820221
2010	0.97122997045517
2011	0.968879997730255
2012	0.985279977321625
2013	0.985740005970001
2014	0.996010005474091
2016	0.993189990520477
2017	0.994140028953552
2018	0.996510028839111
2019	1.00065004825592