Year	gross (GPI)
1981	0.981100022792816
1982	0.988590002059937
1983	0.987049996852875
1984	0.976769983768463
1985	0.983810007572174
1986	0.976740002632141
1987	0.996540009975433
1988	0.982609987258911
1989	0.974839985370636
1990	0.970510005950928
1991	0.971650004386902
1992	0.974370002746582
1993	0.977190017700195
1994	0.976790010929108
1995	0.971979975700378
1996	0.976689994335175
1997	0.983799993991852
1998	0.983020007610321
1999	0.984730005264282
2000	0.990180015563965
2001	0.984669983386993
2002	0.982810020446777
2003	0.975849986076355
2004	0.976890027523041
2005	0.974259972572327
2006	0.9757000207901
2007	0.984499990940094
2008	0.98198002576828
2009	0.982079982757568
2010	0.985159993171692
2011	0.99728000164032
2012	0.997479975223541
2013	0.994340002536774
2014	0.99397999048233
2015	1.00006997585297
2016	1.00147998332977
2017	1.00048005580902
2018	1.0025999546051
2019	1.00777995586395
2020	1.00202000141144