Year Number of 1990 277.87 1991 265.04 1992 254.38 1993 248.43 1994 242.6 1995 247.34 1996 244.55 1997 241.74 1998 256.55 1999 270.5 2000 282.5 2001 298.67 2002 321.05 2003 332.95 2004 357 2005 347.15 2006 343.29 2007 335.01 2008 343.39 2009 354.23 2010 349.87 2011 340.88 2012 333.61 2013 327.61 2014 338.07 2015 336.82 2016 337.87