Year	Percent
1979-01-01	69.9339347560843
1980-01-01	69.0233921450326
1981-01-01	67.6066062382218
1982-01-01	65.7000988009480
1983-01-01	63.0777801035850
1984-01-01	62.1844584649054
1985-01-01	61.3757977806411
1986-01-01	61.9448331849385
1987-01-01	61.3696031680408
1988-01-01	61.6681872419378
1989-01-01	62.6296354159182
1990-01-01	62.8333501553474
1991-01-01	61.7359221336149
1992-01-01	61.5598840784744
1993-01-01	60.3286289855392
1994-01-01	61.4004151719062
1995-01-01	61.4121652093710
1996-01-01	60.4890843647498
1997-01-01	60.2333531062581
1998-01-01	60.5598240559872
1999-01-01	60.4993289534016
2000-01-01	60.8465600298486
2001-01-01	60.5378747906466
2002-01-01	61.9860717331869
2003-01-01	63.4845295834007
2004-01-01	64.6424848626329
2005-01-01	66.1988049937433
2006-01-01	67.2885530154280
2007-01-01	67.6508389967234
2008-01-01	67.6413326227620
2009-01-01	69.2928827663662
2010-01-01	71.2216646574668
2011-01-01	71.6652349280146
2012-01-01	71.7495464271054
2013-01-01	72.1084188998453
2014-01-01	72.1658997830012
2015-01-01	72.7794256549132
2016-01-01	71.9404128967902
2017-01-01	72.7583896612582