Year Number of 1990 2986.82 1991 3222.04 1992 3465.76 1993 3711.28 1994 3975.42 1995 4256.59 1996 4537.01 1997 4786.65 1998 5070.15 1999 5229.97 2000 5314.45 2001 5367.65 2002 5427.89 2003 5492.74 2004 5595.82 2005 5682.01 2006 5737.63 2007 5784.49 2008 5820.99 2009 5874.68 2010 5961.52 2011 6047.32 2012 6120.87 2013 6207.47 2014 6326.89 2015 6486.44 2016 6688.05