Year Number of 1990 164.22 1991 170.5 1992 176.83 1993 182.96 1994 187.5 1995 194.83 1996 203.8 1997 209.83 1998 209.2 1999 210.32 2000 216.58 2001 215.29 2002 222.92 2003 230.44 2004 234.84 2005 239.74 2006 244.19 2007 248.49 2008 254.43 2009 259.21 2010 271.67 2011 282.06 2012 281.32 2013 282.89 2014 287.21 2015 292.02 2016 297.2