Year Number of 1990 352.38 1991 360.83 1992 378.31 1993 392.66 1994 423.96 1995 474.05 1996 475 1997 481.38 1998 481.7 1999 480.91 2000 491.26 2001 492.72 2002 496.26 2003 493.14 2004 497.1 2005 499.42 2006 507.28 2007 511.76 2008 516.96 2009 523.96 2010 540.68 2011 553.21 2012 561.24 2013 578.23 2014 596.71 2015 616.63 2016 637.28