Year Percent 1990-01-01 47.72170000000000000 1991-01-01 41.95620000000000000 1992-01-01 40.66280000000000000 1993-01-01 43.05960000000000000 1994-01-01 43.93840000000000000 1995-01-01 35.34430000000000000 1996-01-01 25.92400000000000000 1997-01-01 19.23780000000000000 1998-01-01 21.47540000000000000 1999-01-01 13.48210000000000000 2000-01-01 1.26632000000000010 2001-01-01 0.73524600000000000 2002-01-01 0.15152200000000000 2003-01-01 0.09356400000000000 2004-01-01 0.11887400000000001 2005-01-01 0.11343299999999999 2006-01-01 0.10275000000000000 2007-01-01 0.17493399999999998 2008-01-01 1.87389000000000000 2009-01-01 5.76603000000000100 2010-01-01 7.04413000000000000 2011-01-01 10.16250000000000000 2012-01-01 11.75520000000000000 2013-01-01 11.21870000000000000