Year	Percent
1979-01-01	55.1245205952825
1980-01-01	55.1212308897524
1981-01-01	56.1041044139247
1982-01-01	57.6068691042286
1983-01-01	58.4624427784209
1984-01-01	58.7613881840406
1985-01-01	59.3349540766107
1986-01-01	58.3630005508554
1987-01-01	58.1965298551411
1988-01-01	57.7393016964734
1989-01-01	56.8224013229752
1990-01-01	56.0994961658811
1991-01-01	56.3840146645302
1992-01-01	56.5267083587185
1993-01-01	56.6624612987435
1994-01-01	55.3908902332599
1995-01-01	54.9567128622994
1996-01-01	54.2458678316596
1997-01-01	54.1833044054412
1998-01-01	53.4512115353146
1999-01-01	53.4154370318964
2000-01-01	51.7620948994966
2001-01-01	51.0407925984039
2002-01-01	49.3573322671848
2003-01-01	47.7469348738238
2004-01-01	46.3999029265451
2005-01-01	44.6645979490111
2006-01-01	42.7366047799366
2007-01-01	41.9033482201201
2008-01-01	41.1527526622968
2009-01-01	38.9449957155485
2010-01-01	37.3598454114574
2011-01-01	36.7369589415457
2012-01-01	36.3728246463688
2013-01-01	36.1587198180746
2014-01-01	35.9636542324259
2015-01-01	35.1281673429563
2016-01-01	34.7586402833828
2017-01-01	33.7184628447912