Year Number of 1990 434.61 1991 450.56 1992 468.85 1993 489.05 1994 509.53 1995 527.66 1996 542.05 1997 551.44 1998 560 1999 570.41 2000 579.79 2001 588.55 2002 597.28 2003 605.37 2004 617.11 2005 628.69 2006 638.97 2007 646.42 2008 654.2 2009 659.9 2010 665.2 2011 674.31 2012 690.58 2013 708.79 2014 726.33 2015 742.53 2016 762.48