Year Number of 1990 27578.42 1991 28883.11 1992 30274.79 1993 31603.44 1994 32860.54 1995 34313.91 1996 35387.32 1997 36508.81 1998 37698.2 1999 38972.04 2000 40022.29 2001 41086.13 2002 42159.26 2003 43250.13 2004 44616.68 2005 46130.79 2006 47086.97 2007 48300.68 2008 49339.01 2009 49946.92 2010 50810.87 2011 51400.77 2012 51611.15 2013 51537.83 2014 50662.77 2015 50795.46 2016 51037.42