Year Percent 1980-01-01 1.4532100000000001 1981-01-01 1.7401400000000002 1982-01-01 3.0258500000000000 1983-01-01 3.9107199999999995 1984-01-01 3.3873500000000000 1985-01-01 3.2227600000000000 1986-01-01 3.7514000000000000 1987-01-01 2.5359300000000000 1988-01-01 2.9002400000000000 1989-01-01 1.5412200000000000 1990-01-01 1.3732000000000000 1991-01-01 0.8229700000000001 1992-01-01 1.1269300000000000 1993-01-01 1.5897200000000000 1994-01-01 1.3073000000000000 1995-01-01 1.2898000000000000 1996-01-01 1.4808600000000000 1997-01-01 1.6776099999999998 1998-01-01 1.9952599999999998 1999-01-01 3.1660100000000000 2000-01-01 4.2351500000000000 2001-01-01 4.8686200000000000 2002-01-01 5.9124000000000000 2003-01-01 7.2570800000000000 2004-01-01 7.9412600000000010 2005-01-01 8.8252500000000000 2006-01-01 9.7256400000000000 2007-01-01 9.1905700000000000 2008-01-01 7.7138800000000005 2009-01-01 7.5303800000000000 2010-01-01 7.9495200000000000 2011-01-01 7.5076100000000010 2012-01-01 7.3664800000000000 2013-01-01 7.8307199999999995 2014-01-01 9.2624800000000000 2015-01-01 9.9023600000000000 2016-01-01 8.7193800000000010