Year Number of 1990 226.23 1991 228.86 1992 247.86 1993 275.76 1994 297.98 1995 302.38 1996 295.27 1997 298.16 1998 306.62 1999 317.64 2000 336.53 2001 339.8 2002 344.56 2003 341.59 2004 341.12 2005 325.46 2006 313.14 2007 298.43 2008 283.1 2009 275.23 2010 271.04 2011 267.59 2012 266.41 2013 269.31 2014 272.79 2015 275.48 2016 278.65