Year	Percent
1968-01-01	46.6101578220346
1969-01-01	47.1324897048406
1970-01-01	46.4832065231241
1971-01-01	47.0833437689373
1972-01-01	49.2626259049972
1973-01-01	49.8134490864670
1974-01-01	52.8811686491564
1975-01-01	54.3388754529714
1976-01-01	55.6821251548564
1977-01-01	55.1924048308536
1978-01-01	55.3591136967123
1979-01-01	55.6535354418734
1980-01-01	56.0333574040772
1981-01-01	56.0668054523958
1982-01-01	56.4287913768108
1983-01-01	55.4951860764611
1984-01-01	55.6276167756016
1985-01-01	56.5907122667160
1986-01-01	56.1832967385209
1987-01-01	56.7457750125839
1988-01-01	56.6785242301531
1989-01-01	55.7993951383637
1990-01-01	55.0692032104429
1991-01-01	54.0866830425206
1992-01-01	53.4513465632988
1993-01-01	53.2902716049990
1994-01-01	52.7562463342448
1995-01-01	52.7161655096956
1996-01-01	52.3718357063116
1997-01-01	52.3481819194611
1998-01-01	52.2577811168244
1999-01-01	53.1362349929076
2000-01-01	53.1917674800863
2001-01-01	53.5829210533994
2002-01-01	55.0646991155148
2003-01-01	55.4555469345161
2004-01-01	55.5877518395196
2005-01-01	54.9078314250561
2006-01-01	54.7659553446216
2007-01-01	55.2874266015731
2008-01-01	55.3406420406454
2009-01-01	55.4019887164246
2010-01-01	56.2928276384129
2011-01-01	56.6193543400931
2012-01-01	58.0002016602125
2013-01-01	56.8437652323138
2014-01-01	56.7568330509095
2015-01-01	57.0811114438513
2016-01-01	55.4421843710711
2017-01-01	54.9613471646566