Year Number of 1990 511.66 1991 577.15 1992 740.79 1993 973.18 1994 1340.9 1995 1903.44 1996 2647.32 1997 3574.64 1998 4030.83 1999 4053.1 2000 3943.04 2001 3747.75 2002 3502.01 2003 3228.07 2004 2573.83 2005 2615.02 2006 3322.89 2007 3687.5 2008 3994.99 2009 4258.65 2010 4502.45 2011 4632.61 2012 4772.67 2013 4889.21 2014 5027.82 2015 5183.03 2016 5325.44