Year	gross (GPI)
1971	0.461809992790222
1972	0.462390005588531
1973	0.469969987869263
1976	0.514140009880066
1977	0.503340005874634
1978	0.500320017337799
1979	0.508650004863739
1980	0.545310020446777
1981	0.534889996051788
1982	0.52658998966217
1986	0.584089994430542
1987	0.577430009841919
1988	0.57506000995636
1989	0.584850013256073
1990	0.596660017967224
1991	0.612559974193573
1992	0.628329992294312
2001	0.671679973602295
2009	0.698159992694855
2011	0.705900013446808
2012	0.714169979095459
2016	0.760950028896332
2017	0.743736445903778