Year	Percent
1979-01-01	40.0115855916667
1980-01-01	41.2433199500000
1981-01-01	41.4191619750000
1982-01-01	40.8360746083333
1983-01-01	40.0273502500000
1984-01-01	41.0028451750000
1985-01-01	42.2187075333333
1986-01-01	44.0861190416667
1987-01-01	44.7128625250000
1988-01-01	45.9201695500000
1989-01-01	47.7182007166667
1990-01-01	48.4864737916667
1991-01-01	47.2229429250000
1992-01-01	46.7830408416667
1993-01-01	46.5315608000000
1994-01-01	47.6701707250000
1995-01-01	49.2535518750000
1996-01-01	49.3598007750000
1997-01-01	49.2561184500000
1998-01-01	49.7054223833333
1999-01-01	50.0555930916667
2000-01-01	51.2021742500000
2001-01-01	51.5005177750000
2002-01-01	51.8354575000000
2003-01-01	52.5713095333333
2004-01-01	52.6027154500000
2005-01-01	53.9942152583333
2006-01-01	54.6864394083333
2007-01-01	55.2894223833333
2008-01-01	55.8711120250000
2009-01-01	55.5732370666667
2010-01-01	55.4610754750000
2011-01-01	55.7411997583333
2012-01-01	55.6406040083333
2013-01-01	55.3971845833333
2014-01-01	55.0466237916667
2015-01-01	55.5341642833333
2016-01-01	55.9213789000000
2017-01-01	56.4571438083333