Year Number of 1990 205.17 1991 209.75 1992 216.31 1993 222.76 1994 230.22 1995 237.07 1996 240.55 1997 245 1998 253.78 1999 263.9 2000 268.28 2001 267.6 2002 268.04 2003 271.24 2004 273.06 2005 276.13 2006 274.87 2007 271.45 2008 267.12 2009 264.84 2010 265.09 2011 267 2012 269.26 2013 271.76 2014 274.5 2015 277.22 2016 280.56