Year	Number
1999	15.14167
2000	21.46739
2001	19.93519
2002	17.75781
2003	17.35766
2004	17.45802
2005	16.38298
2006	10.71154
2007	10.38785
2008	10.42727
2009	10.17917
2010	11.08636
2011	9.39764
2012	10.05645
2013	8.88372
2014	7.93359
2016	7.31541