Year	gross (GPI)
1971	0.914879977703094
1972	0.920549988746643
1973	0.924880027770996
1974	0.929319977760315
1975	0.933719992637634
1976	0.952220022678375
1977	0.952620029449463
1978	0.968479990959167
1979	0.991970002651215
1980	1.0025600194931
1981	1.01170003414154
1982	1.02742004394531
1983	1.03751003742218
1984	1.03708004951477
1985	1.03279995918274
1986	1.03375995159149
1987	1.02339994907379
1988	1.01681995391846
1996	1.0251499414444
2012	1.00409996509552
2013	0.993939995765686
2014	0.994249999523163
2015	0.998780012130737
2016	1.00293004512787
2017	1.00416994094849
2018	1.0073299407959
2019	1.01391994953156
2020	1.01534998416901
2021	1.01925003528595