Year	gross (GPI)
1971	0.57015997171402
1972	0.575399994850159
1973	0.58202999830246
1974	0.582790017127991
1975	0.6042799949646
1976	0.626200020313263
1977	0.641939997673035
1985	0.772069990634918
1988	0.789330005645752
1990	0.818189978599548
1991	0.840560019016266
1992	0.851260006427765
1993	0.865239977836609
1994	0.875789999961853
1995	0.887629985809326
1997	0.912609994411469
1999	0.925949990749359
2000	0.933470010757446
2001	0.936890006065369
2002	0.943650007247925
2003	0.945330023765564
2004	0.960309982299805
2005	0.965290009975433
2006	0.968400001525879
2007	0.988070011138916
2008	0.965590000152588
2009	0.956409990787506
2010	0.954450011253357
2011	0.954029977321625
2012	0.951820015907288
2013	0.97680002450943
2014	0.995530009269714
2015	1.00529003143311
2016	1.01882994174957
2017	1.01710999011993
2020	1.03032994270325