Year	gross (GPI)
1971	0.162039995193481
1972	0.150299996137619
1973	0.206249997019768
1974	0.292380005121231
1975	0.34621998667717
1976	0.383599996566772
1977	0.408389985561371
1978	0.429980009794235
1979	0.462069988250732
1980	0.473159998655319
1981	0.503159999847412
1982	0.538060009479523
1983	0.576489984989166
1984	0.632250010967255
1985	0.690569996833801
1986	0.744660019874573
1987	0.779560029506683
1988	0.807690024375916
1989	0.82956999540329
1990	0.848380029201508
1991	0.887750029563904
1992	0.911040008068085
1993	0.939760029315948
1994	0.963050007820129
1995	0.971830010414124
1996	0.957329988479614
1997	0.985440015792847
1998	0.990490019321442
1999	0.98852002620697
2000	0.978550016880035
2001	0.980979979038239
2002	0.968039989471436
2003	0.960330009460449
2005	0.976189970970154
2006	0.993570029735565
2007	0.990729987621307
2008	0.981450021266937
2009	0.952839970588684
2011	0.985629975795746
2012	0.997399985790253
2013	1.04114997386932
2015	1.01645004749298
2016	0.985549986362457
2017	0.999199986457825
2018	0.990920007228851
2019	0.983060002326965
2020	0.974579989910126
2021	0.960020005702972