Year Number of 1990 338.71 1991 345.67 1992 361.1 1993 374.82 1994 395.6 1995 412.54 1996 420.47 1997 433.28 1998 448.93 1999 447.1 2000 439.22 2001 423.11 2002 410.06 2003 412.82 2004 410.34 2005 411.54 2006 411.39 2007 416.26 2008 421.11 2009 429.57 2010 433.68 2011 438.09 2012 444.3 2013 455.99 2014 464.86 2015 472.27 2016 477.82