Year	Percent
1968-01-01	12.9889411662720
1969-01-01	12.6486685557608
1970-01-01	13.2168220718367
1971-01-01	12.7353258435392
1972-01-01	13.4793254047909
1973-01-01	13.1733941502256
1974-01-01	13.4997446815876
1975-01-01	13.5041571609651
1976-01-01	13.5776234136981
1977-01-01	14.8755315110218
1978-01-01	14.6778625265790
1979-01-01	14.4302516265280
1980-01-01	14.3038271596458
1981-01-01	14.7294210433587
1982-01-01	14.8109025523482
1983-01-01	15.0099910611108
1984-01-01	15.8488371208471
1985-01-01	16.4945835820417
1986-01-01	16.7151051975642
1987-01-01	16.9909787960858
1988-01-01	17.4854917284999
1989-01-01	17.0626075396183
1990-01-01	16.3858584900845
1991-01-01	15.2695701634130
1992-01-01	14.9371765424181
1993-01-01	14.6589129744021
1994-01-01	14.8590483761648
1995-01-01	15.0728448883121
1996-01-01	14.8782701796974
1997-01-01	14.8407720167589
1998-01-01	14.8438749144934
1999-01-01	14.7591188923919
2000-01-01	15.8162241969763
2001-01-01	16.5780378124804
2002-01-01	17.0874600487256
2003-01-01	16.9285952683080
2004-01-01	17.2749552965620
2005-01-01	16.9202443717907
2006-01-01	16.1922931745912
2007-01-01	15.0648301172923
2008-01-01	14.8425272630248
2009-01-01	15.3710569293145
2010-01-01	15.8616803013538
2011-01-01	16.2148268451878
2012-01-01	17.0901055377263
2013-01-01	16.4097667759045
2014-01-01	15.1221803901601
2015-01-01	14.2918161882567
2016-01-01	13.4592874104487
2017-01-01	12.3373035109104