Year	gross (GPI)
1970	0.971840023994446
1971	0.972130000591278
1972	0.972490012645721
1973	0.977050006389618
1974	0.973290026187897
1975	0.978290021419525
1976	0.982150018215179
1977	0.979380011558533
1978	0.98021000623703
1979	0.980170011520386
1980	0.981890022754669
1981	0.986519992351532
1982	0.985469996929169
1983	0.988820016384125
1984	0.988189995288849
1985	0.98879998922348
1986	0.989750027656555
1987	0.990299999713898
1988	0.989149987697601
1989	0.987680017948151
1990	0.987990021705627
1991	0.989700019359589
1992	0.991550028324127
1993	0.989359974861145
1994	0.987240016460419
1995	0.986469984054565
1996	0.987370014190674
1997	0.987039983272552
1998	0.985090017318726
1999	0.98387998342514
2000	0.98429000377655
2001	0.982540011405945
2002	0.98088002204895
2003	0.980090022087097
2004	0.982469975948334
2005	0.982840001583099
2006	0.984600007534027
2007	0.985570013523102
2008	0.987200021743774
2009	0.988430023193359
2010	0.987389981746674
2011	0.987039983272552
2012	0.988919973373413
2013	0.994750022888184
2014	0.995440006256104
2015	0.995389997959137
2016	0.99576997756958
2017	0.990859985351563
2018	0.99260002374649
2019	0.992519974708557
2020	0.99439001083374