Year Number of 1990 264.52 1991 271.04 1992 276.58 1993 287.77 1994 299.19 1995 311.78 1996 327.35 1997 344.51 1998 362.6 1999 378.77 2000 391.32 2001 405.29 2002 427.82 2003 446.67 2004 460.78 2005 478.79 2006 509.18 2007 552.41 2008 608.71 2009 656.3 2010 709.47 2011 690.59 2012 675.72 2013 659.96 2014 650.01 2015 645.56 2016 645.57