Year	Number
1999	15.59096
2002	14.52068
2004	12.22833
2005	10.91835
2006	12.43973
2007	12.01147
2008	12.66297
2009	10.02064
2010	12.24927
2011	10.37682
2012	13.19431
2013	11.21217
2014	11.73893
2015	10.08032
2016	10.60813
2017	13.51165
2018	12.34294