Year Number of 1990 12123.54 1991 12500.78 1992 12668.71 1993 13045.04 1994 13369.36 1995 13684.25 1996 13756.85 1997 14023.92 1998 14029.29 1999 14759.75 2000 14531.24 2001 14542.57 2002 14292.07 2003 15149.29 2004 15154.45 2005 15430.88 2006 15460.24 2007 14974.38 2008 14610.81 2009 16071.06 2010 16530.94 2011 16872.44 2012 16933 2013 17523.45 2014 17534.23 2015 17644.56 2016 17921.94