Year Number of 1990 1640.98 1991 1615.34 1992 1603.35 1993 1567.21 1994 1534.84 1995 1532.86 1996 1544.64 1997 1522.98 1998 1516.68 1999 1502.52 2000 1477.48 2001 1467.27 2002 1470.51 2003 1473.68 2004 1482.47 2005 1493.09 2006 1515.82 2007 1520.38 2008 1519.04 2009 1536.65 2010 1538.98 2011 1518.38 2012 1517.2 2013 1506.72 2014 1483.81 2015 1458.93 2016 1449.76