Year Number of 1990 3171.54 1991 3276.21 1992 3369.3 1993 3525.91 1994 3625.78 1995 3816.55 1996 4023.34 1997 4198.57 1998 4423.37 1999 4681.79 2000 4931.82 2001 5208.41 2002 5513.83 2003 5796.81 2004 6138.8 2005 6499.97 2006 6832.17 2007 7188.26 2008 7586.1 2009 7984.98 2010 8435.05 2011 8606.57 2012 8774.53 2013 8781.05 2014 8562.3 2015 8496.64 2016 8445.26