Year	Percent
1960-01-01	17.907000000000000
1961-01-01	18.414600000000000
1962-01-01	15.966800000000000
1963-01-01	14.748200000000000
1964-01-01	13.304100000000000
1965-01-01	17.728400000000000
1966-01-01	16.865900000000000
1967-01-01	14.669200000000000
1968-01-01	15.723300000000000
1969-01-01	16.050300000000000
1970-01-01	17.526400000000000
1971-01-01	19.004100000000000
1972-01-01	20.139400000000000
1973-01-01	22.354400000000000
1974-01-01	24.287600000000000
1975-01-01	25.946100000000000
1976-01-01	25.520200000000000
1977-01-01	25.454600000000000
1978-01-01	26.729000000000000
1979-01-01	24.096999999999998
1980-01-01	22.991500000000000
1981-01-01	23.718700000000000
1982-01-01	24.253500000000000
1983-01-01	23.817600000000000
1984-01-01	22.611400000000000
1985-01-01	22.065700000000000
1986-01-01	25.576300000000000
1987-01-01	27.200900000000000
1988-01-01	25.007200000000000
1989-01-01	25.841100000000000
1990-01-01	23.815200000000000
1991-01-01	16.740100000000000
1992-01-01	18.366300000000000
1993-01-01	20.468400000000000
1994-01-01	20.946300000000000
1995-01-01	20.850200000000000
1996-01-01	21.686500000000000
1997-01-01	23.022900000000000
1998-01-01	23.353800000000000
1999-01-01	25.384300000000000
2000-01-01	26.583500000000000
2001-01-01	24.346100000000000
2002-01-01	20.289100000000000
2003-01-01	21.832700000000000
2004-01-01	20.886999999999997
2005-01-01	17.154500000000000
2006-01-01	17.672400000000000
2007-01-01	17.833800000000000
2008-01-01	18.226000000000000
2009-01-01	18.434600000000000
2010-01-01	18.899100000000000
2011-01-01	19.960500000000000
2012-01-01	20.252700000000000
2013-01-01	20.831000000000000
2014-01-01	20.910900000000000
2015-01-01	21.029700000000000
2016-01-01	21.694700000000000