Year	gross (GPI)
1974	0.725040018558502
1975	0.816739976406097
1976	0.864610016345978
1977	0.87092000246048
1978	0.866349995136261
1979	0.851809978485107
1980	0.851779997348785
1981	0.845160007476807
1982	0.828809976577759
1983	0.821380019187927
1984	0.825460016727448
1985	0.828429996967316
1986	0.861270010471344
1987	0.873719990253448
1988	0.881359994411469
1989	0.889750003814697
1990	0.899909973144531
1991	0.911360025405884
1992	0.922299981117249
1993	0.927100002765656
1994	0.93639999628067
1995	0.946950018405914
1996	0.957379996776581
1997	0.96696001291275
1998	0.974749982357025
2001	0.991379976272583
2006	0.991980016231537
2007	0.988189995288849
2008	0.984549999237061
2009	0.98351001739502
2010	0.982680022716522
2011	0.984860002994537
2012	0.988900005817413
2013	0.997609972953796
2014	1.00072002410889
2015	1.00246000289917
2016	1.00508999824524
2017	1.00947999954224
2018	1.01135003566742
2019	1.0117199420929
2020	1.00977003574371
2021	1.00856995582581