Year	Percent
1979-01-01	8.25088555833333
1980-01-01	7.93098849166667
1981-01-01	7.48181715833333
1982-01-01	8.58087466666667
1983-01-01	10.44555632500000
1984-01-01	9.54579913333333
1985-01-01	8.82052600833334
1986-01-01	8.77151219166666
1987-01-01	8.69320208333333
1988-01-01	7.96266812500000
1989-01-01	6.89031693333333
1990-01-01	7.23097439166667
1991-01-01	9.21000361666667
1992-01-01	9.98874191666667
1993-01-01	10.05942480833330
1994-01-01	9.42654144166666
1995-01-01	8.16928226666667
1996-01-01	8.29521830833334
1997-01-01	8.13358535833334
1998-01-01	7.39186132500000
1999-01-01	6.71951230833333
2000-01-01	6.12037773333333
2001-01-01	6.49536907500000
2002-01-01	6.22353735833333
2003-01-01	6.02974791666667
2004-01-01	5.59208609166667
2005-01-01	5.27156779166667
2006-01-01	4.97363251666667
2007-01-01	4.84400668333333
2008-01-01	4.62705130833333
2009-01-01	5.48076191666667
2010-01-01	5.46604557500000
2011-01-01	5.39700154166667
2012-01-01	5.43084320000000
2013-01-01	5.72635835833333
2014-01-01	6.29939249166667
2015-01-01	6.21130402500000
2016-01-01	5.92221649166667
2017-01-01	5.82198945000000