Year	number
2005	13.823529411764707
2006	13.8
2007	13.742857142857142
2008	13.771428571428572
2009	13.457142857142857
2010	13.457142857142857
2011	13.4
2012	13.257142857142858
2013	13.117368421052632
2014	13.117368421052632
2015	13.117368421052632
2016	13.012105263157896
2017	13.012105263157896
2018	13.012105263157896
2019	13.012105263157896