Year	Percent
1973-01-01	15.4574
1974-01-01	17.8048
1975-01-01	17.3482
1976-01-01	14.9591
1977-01-01	16.6860
1978-01-01	19.2075
1979-01-01	19.1570
1980-01-01	20.4216
1981-01-01	20.1503
1982-01-01	19.6761
1983-01-01	18.8747
1984-01-01	21.7265
1985-01-01	23.6642
1986-01-01	25.1967
1987-01-01	26.0611
1988-01-01	20.2354
1989-01-01	21.8337
1990-01-01	23.1373
1991-01-01	21.8107
1992-01-01	21.3530
1993-01-01	21.4818
1994-01-01	19.9831
1995-01-01	19.4802
1996-01-01	21.4397
1997-01-01	24.2036
1998-01-01	23.9293
1999-01-01	22.2460
2000-01-01	21.3555
2001-01-01	21.1293
2002-01-01	19.5986
2003-01-01	17.5723
2004-01-01	18.1518
2005-01-01	20.0648
2006-01-01	24.1764
2007-01-01	28.1577
2008-01-01	30.7325
2009-01-01	30.7937
2010-01-01	26.3797
2011-01-01	27.5232
2012-01-01	30.2401
2013-01-01	30.2929
2014-01-01	27.2415
2015-01-01	28.3758
2016-01-01	28.7834