Year Number of 1990 258.89 1991 273.87 1992 289.68 1993 306.51 1994 324.47 1995 343.79 1996 361.1 1997 379.75 1998 399.99 1999 421.48 2000 444.29 2001 456.85 2002 470.12 2003 484.47 2004 499.65 2005 515.78 2006 522.4 2007 529.8 2008 538.5 2009 547.85 2010 557.95 2011 572.71 2012 588.75 2013 605.61 2014 624.21 2015 644.66 2016 665.05