Year	Percent
1999-01-01	34.931
2000-01-01	28.960
2001-01-01	25.540
2002-01-01	25.400
2003-01-01	28.160
2004-01-01	29.690
2005-01-01	27.380
2006-01-01	29.100
2007-01-01	26.810
2008-01-01	16.570
2009-01-01	17.990
2010-01-01	15.150
2011-01-01	13.120
2012-01-01	15.180
2013-01-01	19.710
2014-01-01	19.900
2015-01-01	22.940
2016-01-01	22.700