Year	Percent
1960-01-01	19.7822
1961-01-01	20.1477
1962-01-01	20.9054
1963-01-01	20.6711
1964-01-01	18.7411
1965-01-01	17.7865
1966-01-01	17.4995
1967-01-01	18.2904
1968-01-01	19.5268
1969-01-01	20.8879
1970-01-01	14.7506
1971-01-01	14.8107
1972-01-01	13.3888
1973-01-01	12.0381
1974-01-01	14.6648
1975-01-01	18.9888
1976-01-01	18.7420
1977-01-01	18.1213
1978-01-01	17.4900
1979-01-01	17.3427
1980-01-01	18.0004
1981-01-01	20.5188
1982-01-01	21.6137
1983-01-01	23.0877
1984-01-01	23.4839
1985-01-01	23.4465
1986-01-01	23.4465
1987-01-01	16.4118
1988-01-01	15.3290
1989-01-01	15.3290
1990-01-01	19.6310
1991-01-01	19.0713
1992-01-01	19.0147
1993-01-01	20.9154
1994-01-01	23.1350
1995-01-01	25.4826
1996-01-01	27.8598
1997-01-01	28.5731
1998-01-01	29.6447
1999-01-01	28.3678
2000-01-01	23.7093
2001-01-01	22.1778
2002-01-01	22.0610
2003-01-01	20.8557
2004-01-01	21.5061
2005-01-01	23.2528
2006-01-01	25.7459
2007-01-01	29.9216
2008-01-01	32.1696
2009-01-01	36.4876
2010-01-01	40.5290
2011-01-01	41.7317
2012-01-01	45.5657
2013-01-01	48.0643
2014-01-01	50.0248
2015-01-01	48.7946
2016-01-01	46.1081