Year Number of 1990 12250.86 1991 12692.23 1992 13200.27 1993 13686.89 1994 14142.42 1995 14671.49 1996 15163.96 1997 15652.01 1998 16159.26 1999 16650.78 2000 16902.38 2001 17277.59 2002 17667.79 2003 18146.84 2004 18581.15 2005 19110.96 2006 19466.11 2007 19827.59 2008 20190.25 2009 20434.05 2010 20824.59 2011 21079.93 2012 21847.62 2013 22202.6 2014 22097.83 2015 22356.9 2016 22629.87