Year	Percent
1968-01-01	54.9488327755620
1969-01-01	55.1302059694555
1970-01-01	55.5908380253118
1971-01-01	55.0799289372344
1972-01-01	56.3856005437992
1973-01-01	55.4644645236366
1974-01-01	56.2793939983557
1975-01-01	56.3607690660658
1976-01-01	55.8509816387623
1977-01-01	55.4416295640721
1978-01-01	54.5520882620993
1979-01-01	54.4259397934058
1980-01-01	54.4780643190315
1981-01-01	55.1698366468090
1982-01-01	54.8712028059561
1983-01-01	53.7572336004796
1984-01-01	54.8453233152390
1985-01-01	54.5488564729634
1986-01-01	55.1795866787983
1987-01-01	54.8191882797536
1988-01-01	54.6523482646458
1989-01-01	53.8584264158650
1990-01-01	52.6823600041328
1991-01-01	51.3230076010052
1992-01-01	51.3773802779440
1993-01-01	51.2697838491239
1994-01-01	51.8392418486611
1995-01-01	51.3991442892452
1996-01-01	51.2559163157354
1997-01-01	50.4917753500356
1998-01-01	50.0817980388630
1999-01-01	49.9931526323498
2000-01-01	50.2968391514585
2001-01-01	50.8938010993398
2002-01-01	51.0621974578166
2003-01-01	50.5338029476540
2004-01-01	49.8358633511522
2005-01-01	49.1777508518802
2006-01-01	48.4969403127551
2007-01-01	47.4269723401761
2008-01-01	46.7602114794894
2009-01-01	46.3642506069500
2010-01-01	45.9515456668647
2011-01-01	45.5613496836683
2012-01-01	45.9005831731919
2013-01-01	44.1542522299695
2014-01-01	42.4824064725994
2015-01-01	40.6299110419400
2016-01-01	38.9178961513709
2017-01-01	36.6273820004000