Year Number of 1990 26512.12 1991 25836.62 1992 26284.63 1993 28720.08 1994 29553.93 1995 27162.38 1996 24502.28 1997 22461.5 1998 21495.85 1999 22105.4 2000 22029.18 2001 21683.17 2002 21578.71 2003 21471.5 2004 20968.12 2005 20892.11 2006 19797.97 2007 19503.69 2008 19607.98 2009 18776.5 2010 18715.65 2011 18171.57 2012 17595.15 2013 17385.49 2014 17526.5 2015 18095.98 2016 19011.76