Year	gross (GPI)
1970	0.970960021018982
1971	0.973290026187897
1972	0.984690010547638
1973	0.990260004997253
1974	0.992890000343323
1975	0.983810007572174
1976	0.974139988422394
1977	0.976069986820221
1978	0.976100027561188
1979	0.978340029716492
1980	0.977989971637726
1981	0.97545999288559
1982	0.972859978675842
1983	0.974979996681213
1984	0.975139975547791
1985	0.981800019741058
1986	0.973699986934662
1987	0.97995001077652
1988	0.979330003261566
1989	0.978720009326935
1990	0.975660026073456
1991	0.970939993858337
1992	0.973890006542206
1993	0.970730006694794
1994	0.96425998210907
1995	0.958559989929199
1996	0.957769989967346
1997	0.953920006752014
1998	0.95006000995636
1999	0.952430009841919
2000	0.952149987220764
2001	0.95388001203537
2002	0.948580026626587
2003	0.953719973564148
2004	0.955370008945465
2005	0.95753002166748
2006	0.962159991264343
2007	0.962520003318787
2008	0.967589974403381
2009	0.97026002407074
2010	0.970939993858337
2011	0.968760013580322
2012	0.974020004272461
2013	0.97706001996994
2014	0.97800999879837
2015	0.979579985141754
2016	0.980920016765594
2017	0.981459975242615
2018	0.984679996967316
2019	0.988629996776581
2020	0.989920020103455