Year	Percent
1990-01-01	22.38
1991-01-01	28.48
1992-01-01	28.28
1993-01-01	34.20
1994-01-01	37.49
1995-01-01	35.44
1996-01-01	36.35
1997-01-01	38.06
1998-01-01	39.18
1999-01-01	47.85
2000-01-01	49.03
2001-01-01	51.53
2002-01-01	53.13
2003-01-01	56.42
2004-01-01	56.03
2005-01-01	55.66
2006-01-01	57.49
2007-01-01	60.88
2008-01-01	49.85
2009-01-01	61.93
2010-01-01	62.43
2011-01-01	57.73
2012-01-01	59.69
2013-01-01	61.92
2014-01-01	67.51
2015-01-01	68.98
2016-01-01	69.63