Year	number
2005	17.294117647058822
2006	16.38888888888889
2007	15.88888888888889
2008	14.947368421052632
2009	14.31578947368421
2010	14.368421052631579
2011	14.05
2012	12.9
2013	11.8
2014	11.75
2015	11.15
2016	11.05
2017	11.1
2018	10.95
2019	10.4