Year	Percent
1979-01-01	3.12174845487476
1980-01-01	3.17961709935836
1981-01-01	3.11606233377089
1982-01-01	4.35373534827211
1983-01-01	6.93044468756929
1984-01-01	6.17399844865176
1985-01-01	5.63347970363896
1986-01-01	5.48367231099693
1987-01-01	5.66494155332123
1988-01-01	4.76020778243335
1989-01-01	4.17635011639160
1990-01-01	4.87094179127217
1991-01-01	7.53407986456300
1992-01-01	8.70023361132787
1993-01-01	9.09657809170304
1994-01-01	7.86326968448696
1995-01-01	6.95442094986032
1996-01-01	6.73979924423622
1997-01-01	6.66158161319146
1998-01-01	6.33341739077095
1999-01-01	5.57305297209315
2000-01-01	5.14734801417613
2001-01-01	5.40656500019478
2002-01-01	5.06411367663576
2003-01-01	4.58235556954001
2004-01-01	3.95804263470301
2005-01-01	3.65276872124172
2006-01-01	3.44181885017142
2007-01-01	2.95212207150694
2008-01-01	2.90619988840699
2009-01-01	4.51066556630181
2010-01-01	3.74662170115842
2011-01-01	3.57126595139110
2012-01-01	3.79513934886218
2013-01-01	4.43447439490911
2014-01-01	4.59001383341976
2015-01-01	4.56160266518809
2016-01-01	4.09367928123142
2017-01-01	4.06713777169353