Year Number of 1990 1963.94 1991 2074.36 1992 2188.1 1993 2305.86 1994 2433.04 1995 2573.35 1996 2708.1 1997 2857.39 1998 3029.53 1999 3213.82 2000 3408.69 2001 3549.81 2002 3697.67 2003 3864.68 2004 4033.26 2005 4203.65 2006 4295.18 2007 4382.43 2008 4485.85 2009 4594.17 2010 4710.7 2011 4880.61 2012 5062.07 2013 5256.43 2014 5455.44 2015 5657.31 2016 5862.64