Year Number 1993 29.74639 1994 32.89804 1995 31.8788 1996 35.47525 1997 35.09225 1998 34.37247 1999 34.67901 2000 34.70343 2001 34.59441 2002 34.67576 2003 34.65878 2004 35.15769 2005 33.21247 2006 31.99448 2007 30.83289 2008 29.95208 2009 28.89773 2010 29.85328 2011 31.20174 2012 31.28194 2013 29.00706 2014 29.25521 2015 29.25041 2016 26.80018 2017 25.30846 2018 25.83159