Year	gross (GPI)
1970	1.00583004951477
1971	0.999480009078979
1972	0.990670025348663
1973	0.991540014743805
1974	0.984629988670349
1975	0.985339999198914
1976	0.985189974308014
1977	0.988460004329681
1978	1.00229001045227
1979	0.989629983901978
1980	0.990549981594086
1981	0.986519992351532
1982	0.981689989566803
1984	0.987360000610352
1985	0.994040012359619
1986	0.982379972934723
1987	0.99194997549057
1988	1.04460000991821
1990	0.983500003814697
1991	0.98496001958847
1996	0.984390020370483
1997	0.994459986686707
1998	0.985450029373169
1999	0.996399998664856
2000	0.991039991378784
2001	0.992370009422302
2002	0.993120014667511
2003	0.992860019207001
2004	0.991110026836395
2005	0.990620017051697
2006	0.994090020656586
2007	0.997009992599487
2008	0.995930016040802
2009	0.995450019836426
2010	0.987410008907318
2011	0.988240003585815
2012	0.988229990005493
2013	0.991569995880127
2014	0.997940003871918
2015	0.998809993267059
2016	0.997640013694763
2017	0.99796998500824
2018	1.0010199546814
2019	1.00192999839783
2020	1.00501000881195