Year	gross (GPI)
1970	0.97053998708725
1971	0.968670010566711
1972	0.960020005702972
1973	0.966409981250763
1974	0.970329999923706
1975	0.965229988098145
1976	0.965160012245178
1977	0.9721599817276
1978	0.970979988574982
1979	0.973659992218018
1980	0.978500008583069
1981	0.976999998092651
1982	0.975269973278046
1983	0.972239971160889
1984	0.972060024738312
1985	0.976729989051819
1986	0.979340016841888
1987	0.980960011482239
1988	0.987060010433197
1989	0.98649001121521
1990	0.989099979400635
1991	0.980949997901917
1992	0.980790019035339
1993	0.976989984512329
1994	0.972809970378876
1995	0.972039997577667
1996	0.970459997653961
1997	0.968980014324188
1998	0.966929972171783
1999	0.974889993667603
2000	0.970250010490417
2001	0.970579981803894
2002	0.969760000705719
2003	0.973320007324219
2004	0.973829984664917
2005	0.970489978790283
2006	0.972869992256165
2007	0.974240005016327
2008	0.969690024852753
2009	0.974860012531281
2010	0.969280004501343
2011	0.968869984149933
2012	0.975499987602234
2013	0.975799977779388
2014	0.975759983062744
2015	0.979189991950989
2016	0.980650007724762
2017	0.983420014381409
2018	0.985099971294403
2019	0.985350012779236
2020	0.98224002122879