Year	gross (GPI)
1971	0.99329000711441
1972	0.995970010757446
1973	1.07819998264313
1974	0.996749997138977
1975	0.995959997177124
1976	1.08244001865387
1977	0.987820029258728
1978	0.994319975376129
1979	0.985440015792847
1980	0.989690005779266
1981	0.989579975605011
1982	0.983640015125275
1983	0.986479997634888
1985	0.984019994735718
1986	0.979229986667633
1987	0.984220027923584
1988	0.986679971218109
1989	0.986450016498566
1990	0.981939971446991
1991	0.985080003738403
1992	0.98387998342514
1993	0.984860002994537
1994	0.980199992656708
1995	0.981930017471313
1996	0.984260022640228
1997	0.989019989967346
1998	0.989030003547668
1999	0.988960027694702
2000	0.99074000120163
2001	0.991659998893738
2002	0.992330014705658
2003	0.992579996585846
2004	0.995379984378815
2005	0.990299999713898
2006	0.988749980926514
2007	0.992049992084503
2008	0.989250004291534
2009	0.990390002727509
2010	0.988030016422272
2011	0.995540022850037
2012	0.999409973621368
2013	0.997290015220642
2014	0.995199978351593
2015	0.993780016899109
2016	0.994509994983673
2017	0.994069993495941
2018	0.994050025939941
2019	0.994930028915405
2020	0.992519974708557