Year	Number
1999	15.60879
2002	15.21603
2004	16.56397
2005	17.00291
2006	13.08555
2007	12.50405
2008	12.66736
2009	15.68402
2010	12.01494
2011	11.89104
2012	15.96069
2013	13.59123
2014	13.31944
2015	14.05957
2016	13.10901
2017	14.80638
2018	12.61874