Year	Percent
1960-01-01	21.2957
1961-01-01	18.5425
1962-01-01	16.6438
1963-01-01	18.1424
1964-01-01	19.5222
1965-01-01	19.3051
1966-01-01	18.8182
1967-01-01	18.2105
1968-01-01	18.0281
1969-01-01	18.0090
1970-01-01	14.8494
1971-01-01	15.0616
1972-01-01	15.8759
1973-01-01	18.2303
1974-01-01	19.1392
1975-01-01	20.8469
1976-01-01	22.1834
1977-01-01	20.5193
1978-01-01	29.4545
1979-01-01	39.7167
1980-01-01	42.1187
1981-01-01	43.9733
1982-01-01	47.4551
1983-01-01	47.1929
1984-01-01	48.7095
1985-01-01	45.5837
1986-01-01	47.7905
1987-01-01	38.0075
1988-01-01	37.2308
1989-01-01	36.8345
1990-01-01	43.1025
1991-01-01	48.6129
1992-01-01	39.2530
1993-01-01	34.5275
1994-01-01	28.5963
1995-01-01	24.8986
1996-01-01	20.9308
1997-01-01	17.2895
1998-01-01	17.7886
1999-01-01	21.4253
2000-01-01	24.2530
2001-01-01	28.4467
2002-01-01	31.4481
2003-01-01	35.3918
2004-01-01	42.7639
2005-01-01	39.6564
2006-01-01	30.5729
2007-01-01	26.0683
2008-01-01	20.8868
2009-01-01	15.5187
2010-01-01	14.0366
2011-01-01	14.2624
2012-01-01	15.9663
2013-01-01	19.5082
2014-01-01	23.1105
2015-01-01	26.1329
2016-01-01	27.4676