Year Percent 1987-01-01 0.000000000000000 1988-01-01 0.000000000000000 1989-01-01 0.000000000000000 1990-01-01 0.000000000000000 1991-01-01 0.000000000000000 1992-01-01 0.000000000000000 1993-01-01 0.000000000000000 1994-01-01 0.881777000000000 1995-01-01 1.360170000000000 1996-01-01 1.797970000000000 1997-01-01 2.553850000000000 1998-01-01 4.649870000000000 1999-01-01 5.967830000000000 2000-01-01 5.051470000000000 2001-01-01 6.116640000000000 2002-01-01 7.368130000000001 2003-01-01 9.512120000000000 2004-01-01 12.803700000000000 2005-01-01 19.151200000000000 2006-01-01 22.921000000000000 2007-01-01 24.641400000000000 2008-01-01 22.188200000000000 2009-01-01 13.379000000000001 2010-01-01 7.981550000000000 2011-01-01 6.971170000000000 2012-01-01 6.331220000000000 2013-01-01 7.694770000000000 2014-01-01 9.944339999999999 2015-01-01 11.200400000000000 2016-01-01 12.350000000000000 2017-01-01 12.845200000000000