Year	number
2005	27.333333333333332
2006	28.4375
2007	28.11764705882353
2008	28.457142857142856
2009	28.257142857142856
2010	27.685714285714287
2011	26.37837837837838
2012	27.263157894736842
2013	27.63157894736842
2014	27.605263157894736
2015	27.157894736842106
2016	27.13157894736842
2017	26.81578947368421
2018	26.236842105263158
2019	25.63157894736842