Year	gross (GPI)
1972	0.949010014533997
1973	0.956560015678406
1974	0.953350007534027
1989	0.979300022125244
1990	0.980719983577728
1991	0.984470009803772
1992	0.980090022087097
1993	0.985629975795746
1994	0.98717999458313
1995	0.991100013256073
1996	0.991620004177094
1997	0.979900002479553
1998	0.976559996604919
1999	0.981679975986481
2000	0.985689997673035
2001	0.989319980144501
2002	0.991500020027161
2003	0.994040012359619
2004	0.994509994983673
2005	0.994449973106384
2006	0.99456000328064
2007	0.993480026721954
2008	0.991169989109039
2009	0.990379989147186
2010	0.991819977760315
2011	0.996070027351379
2012	1.00168001651764
2013	1.00181996822357
2014	1.00218999385834
2017	1.00057995319366
2018	0.988590002059937
2019	0.986989974975586
2020	0.96372002363205