Year Percent 1980-01-01 2.7258500000000000 1981-01-01 2.5715900000000000 1982-01-01 2.5051900000000002 1983-01-01 2.3827500000000000 1984-01-01 2.2853400000000000 1985-01-01 2.6927500000000000 1986-01-01 2.5168200000000000 1987-01-01 2.2323300000000000 1988-01-01 1.4975700000000000 1989-01-01 0.9756950000000001 1990-01-01 2.3398900000000000 1991-01-01 2.1995200000000000 1992-01-01 7.1259300000000000 1993-01-01 8.7974100000000010 1994-01-01 9.2294900000000000 1995-01-01 8.8844600000000000 1996-01-01 11.9225000000000000 1997-01-01 15.0748000000000000 1998-01-01 19.6123000000000000 1999-01-01 21.4408000000000000 2000-01-01 22.3595000000000000 2001-01-01 24.1076000000000000 2002-01-01 27.5499000000000000 2003-01-01 31.4511000000000000 2004-01-01 29.7283000000000000 2005-01-01 27.9197000000000000 2006-01-01 25.9016000000000000 2007-01-01 21.2969000000000000 2008-01-01 17.9846000000000000 2009-01-01 21.1046000000000000 2010-01-01 19.6647000000000000 2011-01-01 18.3692000000000000 2012-01-01 17.8980000000000000 2013-01-01 16.6546000000000000 2014-01-01 16.1156000000000000 2015-01-01 16.7251000000000000 2016-01-01 15.7316000000000000