Year	Number
2003	20.50513
2004	21.24369
2005	21.35578
2006	19.98416
2007	18.6999
2008	17.85879
2009	20.18442
2010	17.22447
2011	15.54582
2012	18.65821
2013	18.1747
2014	16.89397
2015	16.69
2016	17.83561