Year Number of 1990 1592.51 1991 1559.12 1992 1534.25 1993 1511.33 1994 1498.47 1995 1484.96 1996 1479.15 1997 1474.55 1998 1476.38 1999 1477.26 2000 1471.66 2001 1477.6 2002 1490.21 2003 1499.59 2004 1501.49 2005 1511.66 2006 1524.61 2007 1541.29 2008 1559.23 2009 1576.87 2010 1597.09 2011 1621.57 2012 1649.25 2013 1662.61 2014 1670.96 2015 1702.55 2016 1736.58