Year	Number
1999	20.65672
2005	19.51643
2006	10.42339
2008	12.03436
2009	12.03755
2010	14.59868
2011	16.57551
2012	14.23343
2013	9.50526
2014	10.55754
2015	9.91451
2016	8.01059
2017	7.90193
2018	7.85949