Year	Number of Years
1973-01-01	74.4975609756098
1978-01-01	75.9853658536586
1986-01-01	75.2658536585366
1987-01-01	75.4658536585366
1988-01-01	75.7146341463415
1989-01-01	75.9146341463415
1990-01-01	76.1146341463415
1991-01-01	76.4146341463415
1992-01-01	76.6146341463415
1993-01-01	76.9146341463415
1994-01-01	77.1658536585366
1995-01-01	77.4170731707317
1996-01-01	77.6195121951220
1997-01-01	77.8219512195122
1998-01-01	78.0268292682927
1999-01-01	78.2804878048781
2000-01-01	78.4853658536586
2001-01-01	78.6390243902439
2002-01-01	78.8414634146341
2003-01-01	78.9414634146341
2004-01-01	79.1414634146342
2005-01-01	79.3414634146342
2006-01-01	79.6390243902439
2007-01-01	79.8878048780488
2008-01-01	80.1878048780488
2009-01-01	80.3878048780488
2010-01-01	80.6365853658537
2011-01-01	80.8878048780488
2012-01-01	81.1878048780488
2013-01-01	81.4390243902439
2014-01-01	81.6902439024390
2015-01-01	81.9902439024390
2016-01-01	82.2414634146342