Year	gross (GPI)
1973	0.79092001914978
1974	0.785440027713776
1975	0.854229986667633
1976	0.890079975128174
1977	0.895290017127991
1978	0.889249980449677
1979	0.881009995937347
1980	0.881240010261536
1981	0.876659989356995
1982	0.869910001754761
1983	0.871140003204346
1984	0.875509977340698
1985	0.878340005874634
1986	0.898370027542114
1987	0.906899988651276
1988	0.913770020008087
1989	0.922060012817383
1990	0.928219974040985
1991	0.939369976520538
1992	0.947839975357056
1993	0.948430001735687
1994	0.954779982566834
1995	0.958589971065521
1996	0.96372002363205
1997	0.97010999917984
1998	0.971499979496002
1999	0.976920008659363
2000	0.98114001750946
2001	0.986129999160767
2002	0.986940026283264
2003	0.988640010356903
2004	0.991559982299805
2005	0.988300025463104
2006	0.986459970474243
2007	0.983759999275208
2008	0.98523998260498
2009	0.984229981899261
2010	0.992449998855591
2011	0.994520008563995
2012	0.991890013217926
2013	0.994690001010895
2014	0.994809985160828
2015	0.993099987506866
2016	0.995689988136292
2017	0.996990025043488
2018	0.997959971427917
2019	0.998080015182495
2020	0.996999979019165