Year	gross (GPI)
1971	0.712029993534088
1972	0.732280015945435
1973	0.739709973335266
1974	0.750509977340698
1975	0.753009974956512
1976	0.763960003852844
1977	0.771650016307831
1978	0.775139987468719
1979	0.785449981689453
1980	0.790489971637726
1981	0.790120005607605
1982	0.795090019702911
1983	0.794430017471313
1984	0.797749996185303
1985	0.7985799908638
1986	0.804620027542114
1987	0.810859978199005
1988	0.814869999885559
1989	0.817879974842072
1990	0.822260022163391
1991	0.828980028629303
1992	0.872099995613098
1995	0.847949981689453
1997	0.85505998134613
1998	0.806869983673096
1999	0.826870024204254
2001	0.853860020637512
2002	0.800729990005493
2003	0.848169982433319
2004	0.841090023517609
2005	0.826460003852844
2006	0.828119993209839
2007	0.837960004806519
2008	0.842559993267059
2009	0.856209993362427
2011	0.861349999904633
2012	0.869220018386841
2014	0.876999974250793
2015	0.883459985256195
2016	0.885640025138855
2017	0.889527857303619
2018	0.889680445194244