Year	Percent of Total
1960-01-01	53.9000323141627
1961-01-01	53.8170074001409
1962-01-01	53.8227967327880
1963-01-01	53.8779009320321
1964-01-01	53.9448991811460
1965-01-01	54.0084432380975
1966-01-01	53.7677346176742
1967-01-01	53.6047543933293
1968-01-01	53.4926584309354
1969-01-01	53.4024915816466
1970-01-01	53.3163432919784
1971-01-01	53.0339450153319
1972-01-01	52.7800108719532
1973-01-01	52.5611879279094
1974-01-01	52.4073528490215
1975-01-01	52.3437672961693
1976-01-01	52.2236459521950
1977-01-01	52.1262944127410
1978-01-01	52.0235576070153
1979-01-01	51.8816471450635
1980-01-01	51.6817431316546
1981-01-01	51.3605041022929
1982-01-01	51.1348270590978
1983-01-01	50.9886894864094
1984-01-01	50.9107500503368
1985-01-01	50.8867633784353
1986-01-01	50.7211413477402
1987-01-01	50.6268128805085
1988-01-01	50.5770066560931
1989-01-01	50.5564992448274
1990-01-01	50.5633637504534
1991-01-01	50.3978867741595
1992-01-01	50.2998677503353
1993-01-01	50.2589993349144
1994-01-01	50.2652995141376
1995-01-01	50.3166138194671
1996-01-01	50.2428799603375
1997-01-01	50.2182153929919
1998-01-01	50.2385484915626
1999-01-01	50.3072878002237
2000-01-01	50.4224763689424
2001-01-01	50.3597114634432
2002-01-01	50.3859401946109
2003-01-01	50.4696358449574
2004-01-01	50.5857581042020
2005-01-01	50.7352651475099
2006-01-01	50.9150135644344
2007-01-01	51.1497059230899
2008-01-01	51.4507814712316
2009-01-01	51.8211715515079
2010-01-01	52.2480159383973
2011-01-01	52.7489974208510
2012-01-01	53.2627185422797
2013-01-01	53.7924979631717
2014-01-01	54.3425152403632
2015-01-01	54.9088501197315
2016-01-01	55.3942242193300
2017-01-01	55.9201273567672