Year	Percent
1978-01-01	21.490100000000000
1979-01-01	20.761000000000000
1980-01-01	23.425400000000000
1981-01-01	18.606100000000000
1982-01-01	16.388100000000000
1983-01-01	17.679900000000000
1984-01-01	20.344100000000000
1985-01-01	21.537500000000000
1986-01-01	22.029400000000000
1987-01-01	22.100300000000000
1988-01-01	26.517000000000000
1989-01-01	28.630800000000000
1990-01-01	21.351300000000000
1991-01-01	23.035500000000000
1992-01-01	22.721000000000000
1993-01-01	22.068000000000000
1994-01-01	20.541100000000000
1995-01-01	19.600300000000000
1996-01-01	19.515600000000000
1997-01-01	19.457300000000000
1998-01-01	18.375999999999998
1999-01-01	17.494700000000000
2000-01-01	20.203600000000000
2001-01-01	18.576300000000000
2002-01-01	16.119700000000000
2003-01-01	17.197700000000000
2004-01-01	18.247300000000000
2005-01-01	19.771900000000000
2006-01-01	24.166900000000000
2007-01-01	26.530100000000000
2008-01-01	25.846900000000000
2009-01-01	28.499600000000000
2010-01-01	28.995800000000000
2011-01-01	26.918400000000000
2012-01-01	29.852400000000000
2013-01-01	33.800200000000000
2014-01-01	36.050300000000000
2015-01-01	35.991400000000000
2016-01-01	38.455400000000000