Year	Number of Years
1991-01-01	71.4878048780488
1997-01-01	72.0390243902439
2000-01-01	71.5829268292683
2001-01-01	72.2341463414634
2002-01-01	72.2853658536585
2003-01-01	72.4365853658537
2004-01-01	72.6829268292683
2005-01-01	72.8341463414634
2006-01-01	73.3853658536585
2007-01-01	73.6317073170732
2008-01-01	73.8853658536585
2009-01-01	73.9853658536586
2010-01-01	74.3365853658537
2011-01-01	74.5365853658537
2012-01-01	74.8365853658537
2013-01-01	75.1853658536585
2014-01-01	75.3365853658537
2015-01-01	75.2878048780488
2016-01-01	75.2390243902439