Year Number of 1990 187.25 1991 185.05 1992 191.08 1993 190.62 1994 192.24 1995 187.9 1996 183.75 1997 179.57 1998 180.22 1999 183.95 2000 189.1 2001 193.45 2002 202.49 2003 219.01 2004 229.74 2005 238.7 2006 246.55 2007 258.19 2008 272.02 2009 280.62 2010 287.63 2011 287.3 2012 303 2013 293.51 2014 297.42 2015 304.23 2016 307.48