2017 6.79671232876712
2016 6.65191256830601
2015 4.08219178082192
2014 4.58027397260274
2013 7.26356164383562
2012 5.10273224043716
2011 7.6027397260274
2010 7.11835616438356
2009 6.43616438356164
2008 6.37540983606557
2007 5.34849315068493
2006 5.55917808219178
2005 8.27287671232877
2004 9.03606557377049
2003 9.70909090909091
2002 NA
2001 NA