Year	Number
1998	12.48995
1999	12.84484
2001	13.26337
2002	12.63283
2003	11.01028
2004	10.8593
2005	10.71627
2006	10.37342
2007	11.27929
2008	10.66826
2009	11.43411
2010	10.81463
2012	9.98272
2013	10.11683
2014	10.76287
2015	11.37105
2016	10.94839
2017	11.22574
2018	11.66252