Year	Percent
1968-01-01	23.6119
1969-01-01	23.4787
1970-01-01	16.1559
1971-01-01	17.4594
1972-01-01	18.3140
1973-01-01	18.2247
1974-01-01	18.8217
1975-01-01	18.5828
1976-01-01	17.8416
1977-01-01	18.2811
1978-01-01	19.0440
1979-01-01	22.0981
1980-01-01	27.0053
1981-01-01	26.8766
1982-01-01	26.7096
1983-01-01	26.8761
1984-01-01	25.8641
1985-01-01	22.9504
1986-01-01	22.7551
1987-01-01	21.6647
1988-01-01	18.8290
1989-01-01	20.1435
1990-01-01	21.1455
1991-01-01	22.1895
1992-01-01	24.1474
1993-01-01	28.6447
1994-01-01	28.1749
1995-01-01	28.0090
1996-01-01	26.8916
1997-01-01	23.4234
1998-01-01	16.2714
1999-01-01	13.4097
2000-01-01	13.5921
2001-01-01	14.0443
2002-01-01	14.7587
2003-01-01	15.2294
2004-01-01	15.5294
2005-01-01	17.7124
2006-01-01	18.5984
2007-01-01	19.8334
2008-01-01	20.4316
2009-01-01	21.8476
2010-01-01	22.7168
2011-01-01	22.9526
2012-01-01	22.7773
2013-01-01	21.7581
2014-01-01	22.0435
2015-01-01	22.6279
2016-01-01	21.7788