Year Number of 1990 458.28 1991 464.05 1992 470.29 1993 473.2 1994 478.39 1995 483.67 1996 488.06 1997 492.67 1998 503.12 1999 517.25 2000 530.36 2001 543.33 2002 555.67 2003 578.73 2004 578.05 2005 583.74 2006 591.9 2007 605.11 2008 615.69 2009 623.08 2010 626.03 2011 638.07 2012 649.55 2013 658.62 2014 667.8 2015 674.85 2016 683.36