Year	gross (GPI)
1970	0.967029988765717
1971	0.964800000190735
1972	0.955370008945465
1973	0.962459981441498
1974	0.967440009117126
1975	0.962019979953766
1976	0.961749970912933
1977	0.969879984855652
1978	0.968039989471436
1979	0.971610009670258
1980	0.976979970932007
1981	0.974889993667603
1982	0.973110020160675
1983	0.969150006771088
1984	0.970610022544861
1985	0.975989997386932
1986	0.978779971599579
1987	0.980449974536896
1988	0.986890017986298
1989	0.985970020294189
1990	0.989030003547668
1991	0.980369985103607
1992	0.980719983577728
1993	0.976599991321564
1994	0.971889972686768
1995	0.971010029315948
1996	0.969210028648376
1997	0.967890024185181
1998	0.96561998128891
1999	0.974370002746582
2000	0.969030022621155
2001	0.969399988651276
2002	0.968569993972778
2003	0.972729980945587
2004	0.973969995975494
2005	0.97010999917984
2006	0.972959995269775
2007	0.974720001220703
2008	0.969690024852753
2009	0.975359976291656
2010	0.968710005283356
2011	0.968089997768402
2012	0.975090026855469
2013	0.975130021572113
2014	0.975319981575012
2015	0.979430019855499
2016	0.981010019779205
2017	0.984099984169006
2018	0.985960006713867
2019	0.986199975013733
2020	0.982829988002777