Year	gross (GPI)
1971	0.855840027332306
1972	0.883279979228973
1973	0.868059992790222
1974	0.880689978599548
1976	0.895089983940125
1977	0.886189997196198
1978	0.892149984836578
1981	0.913139998912811
1982	0.909739971160889
1983	0.910719990730286
1984	0.901009976863861
1985	0.906319975852966
1986	0.91949999332428
1987	0.911530017852783
1988	0.914520025253296
1989	0.919210016727448
1990	0.924070000648499
1991	0.938929975032806
1992	0.938279986381531
1993	0.936039984226227
1994	0.94310998916626
1995	0.938870012760162
1999	0.968159973621368
2000	0.97477000951767
2001	0.978020012378693
2002	0.989260017871857
2003	0.99167001247406
2004	0.993740022182465
2005	1.00077998638153
2006	0.989790022373199
2008	0.993260025978088
2009	0.982749998569489
2010	0.990069985389709
2014	0.971369981765747
2016	0.96849000453949
2017	0.946460008621216
2018	0.95550000667572