Year	gross (GPI)
1980	0.947939991950989
1981	0.949949979782104
1982	0.957300007343292
1983	0.961409986019135
1984	0.964129984378815
1985	0.968529999256134
1986	0.970610022544861
1987	0.970019996166229
1988	0.971080005168915
1989	0.971740007400513
1990	0.972699999809265
1991	0.973070025444031
1992	0.975359976291656
1993	0.97843998670578
1994	0.976520001888275
1995	0.975660026073456
1996	0.972670018672943
1997	0.971769988536835
1998	0.969739973545074
1999	0.969780027866364
2000	0.968559980392456
2001	0.971449971199036
2002	0.973890006542206
2003	0.977989971637726
2004	0.98088002204895
2005	0.981260001659393
2006	0.984589993953705
2007	0.986479997634888
2008	0.989030003547668
2009	0.991980016231537
2010	0.994599997997284
2011	0.996389985084534
2012	0.995119988918304
2013	0.997959971427917
2014	0.999920010566711
2015	0.999520003795624
2016	0.998839974403381
2017	0.996249973773956
2018	0.993879973888397
2019	0.994360029697418
2020	0.993229985237122