Year	Percent
1960-01-01	19.6814
1961-01-01	20.2878
1962-01-01	21.5847
1963-01-01	21.1294
1964-01-01	19.3520
1965-01-01	19.1954
1966-01-01	18.6896
1967-01-01	19.1529
1968-01-01	19.5838
1969-01-01	20.1418
1970-01-01	13.9639
1971-01-01	13.6673
1972-01-01	13.1373
1973-01-01	13.6082
1974-01-01	14.0916
1975-01-01	15.9839
1976-01-01	17.1641
1977-01-01	17.8572
1978-01-01	17.4691
1979-01-01	16.9728
1980-01-01	17.3067
1981-01-01	19.8498
1982-01-01	20.6767
1983-01-01	21.4199
1984-01-01	21.1435
1985-01-01	20.8868
1986-01-01	20.8868
1987-01-01	17.5676
1988-01-01	16.0299
1989-01-01	16.0299
1990-01-01	18.2858
1991-01-01	18.9119
1992-01-01	20.2033
1993-01-01	21.2081
1994-01-01	22.9414
1995-01-01	24.9782
1996-01-01	26.1277
1997-01-01	26.2216
1998-01-01	27.0206
1999-01-01	27.4505
2000-01-01	25.9004
2001-01-01	19.6479
2002-01-01	14.2118
2003-01-01	14.3537
2004-01-01	14.6034
2005-01-01	15.9230
2006-01-01	16.9917
2007-01-01	17.5709
2008-01-01	17.2138
2009-01-01	17.6745
2010-01-01	18.5300
2011-01-01	19.2012
2012-01-01	20.7549
2013-01-01	22.3947
2014-01-01	23.6212
2015-01-01	35.8909
2016-01-01	48.0666