Year Number of 1990 3530.31 1991 3720.22 1992 3798.78 1993 3905.64 1994 4064.54 1995 4260.25 1996 4350.7 1997 4585.73 1998 4603.98 1999 4626.03 2000 4710.14 2001 4810.09 2002 4915.03 2003 5063.7 2004 5202.39 2005 5417.43 2006 5662.16 2007 5933.01 2008 6150.11 2009 6462.43 2010 6597.38 2011 6741.28 2012 6932.81 2013 7021.12 2014 7045.15 2015 6955.56 2016 6933.59