Year Number of 1990 531.37 1991 520.02 1992 513.52 1993 495.02 1994 484.3 1995 475.98 1996 483.95 1997 490.57 1998 486.11 1999 494.16 2000 510.23 2001 518.81 2002 528.81 2003 533.62 2004 543.69 2005 552.59 2006 564.53 2007 574.43 2008 582.41 2009 592.06 2010 608.13 2011 618.49 2012 628.4 2013 645.43 2014 664.32 2015 685.79 2016 708.12