Year	Percent
1979-01-01	51.8054931512459
1980-01-01	52.9720542015985
1981-01-01	53.6336393349358
1982-01-01	54.0001872600478
1983-01-01	53.8922885796823
1984-01-01	55.2989013631725
1985-01-01	57.2545604570216
1986-01-01	60.4212047182462
1987-01-01	61.5559607850740
1988-01-01	63.3338367905900
1989-01-01	65.2248246349077
1990-01-01	66.7838156282678
1991-01-01	67.0574254499746
1992-01-01	67.2831952512371
1993-01-01	67.1333219065555
1994-01-01	67.7381913816611
1995-01-01	69.0095481133265
1996-01-01	69.0298200706765
1997-01-01	69.3169402546236
1998-01-01	69.3157335709373
1999-01-01	69.3784307909519
2000-01-01	70.4600341582708
2001-01-01	71.1171610416854
2002-01-01	71.5621540336754
2003-01-01	72.4916644324282
2004-01-01	71.8584526250080
2005-01-01	73.6762408716989
2006-01-01	74.2116496143394
2007-01-01	74.7847481293994
2008-01-01	75.3783743206027
2009-01-01	75.5494925448771
2010-01-01	75.1449224635999
2011-01-01	75.6354245677608
2012-01-01	75.5652014360372
2013-01-01	75.8024059459157
2014-01-01	75.8699059661864
2015-01-01	76.5765186122476
2016-01-01	76.8747648897207
2017-01-01	77.6863129337821