Year	gross (GPI)
1991	0.990750014781952
1992	0.993359982967377
1993	0.995739996433258
1994	0.998149991035461
1995	0.999180018901825
1996	1.00031995773315
1997	1.00139999389648
1998	0.990239977836609
1999	0.984489977359772
2000	0.986720025539398
2001	0.993510007858276
2002	0.996159970760345
2003	0.988399982452393
2004	0.988929986953735
2005	0.988619983196259
2006	0.988979995250702
2007	0.994000017642975
2008	0.993210017681122
2009	0.993489980697632
2010	0.991289973258972
2011	0.991289973258972
2012	0.990190029144287
2013	0.985570013523102
2014	0.990450024604797
2015	0.992009997367859
2016	0.988650023937225
2017	0.994229972362518
2018	0.996760010719299
2019	0.99533998966217
2020	0.996540009975433