Year	gross (GPI)
1971	0.998740017414093
1972	0.992049992084503
1973	0.990700006484985
1974	0.981079995632172
1975	0.986940026283264
1976	0.993040025234222
1977	0.999279975891113
1978	1.0045599937439
1979	1.00771999359131
1980	1.01374995708466
1981	1.00533998012543
1982	1.01039004325867
1983	0.998269975185394
1984	0.990019977092743
1985	0.991419970989227
1986	0.990320026874542
1987	0.988659977912903
1988	0.984220027923584
1989	0.986029982566834
1990	0.998310029506683
1991	0.998470008373261
1992	0.994520008563995
1993	1
1994	0.999369978904724
1995	0.996630012989044
1996	0.994480013847351
1997	1.00078999996185
1999	0.995660006999969
2000	1.00177001953125
2001	1.00236999988556
2002	1.00156998634338
2003	1.0035799741745
2004	0.99507999420166
2005	0.998709976673126
2006	0.997009992599487
2007	0.99251002073288
2008	0.988629996776581
2009	0.988839983940125
2010	1.00018000602722
2011	0.99220997095108
2012	0.997699975967407
2013	1.00226998329163
2014	1.00852000713348
2015	0.999809980392456
2016	1.0035400390625
2017	1.00108003616333
2018	0.99115002155304
2019	0.993120014667511
2020	0.99371999502182