Year Number of 1990 353.72 1991 374.26 1992 397.85 1993 424.43 1994 454.03 1995 486.82 1996 490.96 1997 496.33 1998 502.69 1999 510.26 2000 519.17 2001 521.53 2002 525.42 2003 530.61 2004 537.06 2005 544.7 2006 557.06 2007 570.64 2008 585.55 2009 601.54 2010 618.74 2011 637.58 2012 658.03 2013 679.57 2014 702.48 2015 726.82 2016 752.73