Year	gross (GPI)
1975	0.979480028152466
1976	0.943189978599548
1978	0.970430016517639
1979	0.978330016136169
1980	0.950820028781891
1981	0.953199982643127
1982	0.97136002779007
1983	0.982879996299744
1984	0.965510010719299
1985	0.970430016517639
1986	0.988870024681091
1987	0.991089999675751
1991	0.993560016155243
1992	1.00638997554779
1993	1.0137300491333
1994	1.03576004505157
1995	1.02603995800018
1996	1.0141099691391
1997	1.02841997146606
1998	1.02120995521545
1999	1.01259994506836
2000	1.0135999917984
2001	1.01298999786377
2002	1.01331996917725
2003	1.00248003005981
2004	0.994840025901794
2005	0.999859988689423
2006	0.998610019683838
2007	0.993929982185364
2008	0.986440002918243
2009	0.983380019664764
2010	0.97732812166214
2011	0.976038575172424
2012	0.971928298473358
2013	0.971923232078552
2014	0.980029046535492
2015	0.981966078281403
2016	0.982713043689728
2017	0.981526672840118
2018	0.979489028453827
2019	0.979250073432922
2020	0.978658974170685
2021	0.977841675281525