Year	Percent
1997-01-01	23.4779
1998-01-01	22.9072
1999-01-01	24.1190
2000-01-01	21.0176
2001-01-01	29.8607
2002-01-01	37.2409
2003-01-01	38.8427
2004-01-01	45.6895
2005-01-01	44.3251
2006-01-01	48.8163
2007-01-01	54.4031
2008-01-01	56.5123
2009-01-01	56.7006
2010-01-01	56.7078
2011-01-01	55.7739
2012-01-01	56.1473
2013-01-01	57.9896
2014-01-01	61.0851
2015-01-01	62.8506
2016-01-01	64.7653