Year	gross (GPI)
1971	0.981379985809326
1972	0.98335999250412
1973	0.979510009288788
1974	0.981270015239716
1989	1.0006799697876
1990	0.997229993343353
1991	1.00666999816895
1992	1.00088000297546
1993	0.997359991073608
1994	0.997460007667542
1995	0.997680008411407
1996	0.996299982070923
1997	0.99533998966217
1998	0.991869986057281
1999	0.989449977874756
2000	0.987649977207184
2001	0.98377001285553
2002	0.981819987297058
2003	0.981509983539581
2004	0.985459983348846
2005	0.986599981784821
2006	0.989180028438568
2007	0.990899980068207
2008	0.983399987220764
2009	0.984969973564148
2010	0.983669996261597
2011	0.98225998878479
2012	0.981060028076172
2015	0.985080003738403
2016	0.987460017204285
2017	0.986720025539398
2018	0.991530001163483
2019	0.990320026874542
2020	0.99057000875473