Year	Percent
1979-01-01	46.4339072000000
1980-01-01	47.8956334583333
1981-01-01	48.2235916083333
1982-01-01	47.6265350750000
1983-01-01	46.7627670333333
1984-01-01	48.0113318333333
1985-01-01	49.5509824333333
1986-01-01	51.8386150250000
1987-01-01	52.6517529916667
1988-01-01	54.1761064000000
1989-01-01	56.4157947916667
1990-01-01	57.3747004583333
1991-01-01	55.9626325500000
1992-01-01	55.5990228333333
1993-01-01	55.4404125916667
1994-01-01	56.8590596500000
1995-01-01	58.7906149500000
1996-01-01	58.9595601000000
1997-01-01	58.8420445500000
1998-01-01	59.4029779583333
1999-01-01	59.8520385333333
2000-01-01	61.2659035333333
2001-01-01	61.6527082333333
2002-01-01	62.0378693666667
2003-01-01	62.9792160000000
2004-01-01	63.0051731500000
2005-01-01	64.5948027416667
2006-01-01	65.4451223833333
2007-01-01	66.0605538416667
2008-01-01	66.7180796000000
2009-01-01	66.3023551166667
2010-01-01	66.1460692916667
2011-01-01	66.6510925083333
2012-01-01	66.5697122916667
2013-01-01	66.4196866500000
2014-01-01	66.1024632250000
2015-01-01	66.8374341750000
2016-01-01	67.3951521750000
2017-01-01	68.1482963583334