Year	Percent
1975-01-01	39.1755
1976-01-01	36.4626
1977-01-01	36.9316
1978-01-01	35.9215
1979-01-01	39.3914
1980-01-01	38.7217
1981-01-01	34.6897
1982-01-01	36.1141
1983-01-01	37.9029
1984-01-01	35.5389
1985-01-01	37.1424
1986-01-01	40.3523
1987-01-01	43.2199
1988-01-01	46.0458
1989-01-01	51.8309
1990-01-01	53.0889
1991-01-01	53.8286
1992-01-01	52.1796
1993-01-01	54.8989
1994-01-01	58.1188
1995-01-01	56.8380
1996-01-01	58.6459
1997-01-01	60.1895
1998-01-01	63.0655
1999-01-01	67.7756
2000-01-01	72.4332
2001-01-01	70.8945
2002-01-01	69.9457
2003-01-01	67.8494
2004-01-01	65.2225
2005-01-01	64.6568
2006-01-01	59.7807
2007-01-01	59.6458
2008-01-01	60.3677
2009-01-01	61.7534
2010-01-01	63.1150
2011-01-01	65.6872
2012-01-01	66.4578
2013-01-01	67.8789
2014-01-01	72.5772
2015-01-01	73.5374
2016-01-01	73.7541