Year Number of 1990 141.12 1991 143.69 1992 146.42 1993 148.92 1994 151.58 1995 153.67 1996 158.82 1997 166.89 1998 176.08 1999 188.41 2000 205.09 2001 219.44 2002 233.81 2003 252.73 2004 274.75 2005 296.67 2006 317.99 2007 337.94 2008 350.62 2009 366.3 2010 379.53 2011 390.25 2012 401.81 2013 415.29 2014 428.99 2015 443.49 2016 457.09