Year Percent 1990-01-01 2.3382900000000000 1991-01-01 3.4287900000000002 1992-01-01 8.9698000000000000 1993-01-01 18.4503000000000000 1994-01-01 24.0802000000000000 1995-01-01 24.4485000000000000 1996-01-01 26.9204000000000000 1997-01-01 28.4458000000000000 1998-01-01 30.1577000000000000 1999-01-01 32.3810000000000000 2000-01-01 32.9026000000000000 2001-01-01 35.9550000000000000 2002-01-01 39.6777000000000000 2003-01-01 43.3885000000000000 2004-01-01 44.8899000000000000 2005-01-01 42.1077000000000000 2006-01-01 41.6269000000000000 2007-01-01 47.3408000000000000 2008-01-01 45.0448000000000000 2009-01-01 50.0698000000000000 2010-01-01 40.3980000000000000 2011-01-01 29.2008000000000000 2012-01-01 44.6010000000000060 2013-01-01 47.7103000000000000 2014-01-01 45.6710000000000100 2015-01-01 50.1875000000000000 2016-01-01 53.1602000000000000