Year	number
2005	24.6
2006	23.1875
2007	23.0625
2008	22.5
2009	21.823529411764707
2010	20.941176470588236
2011	20
2012	19.75
2013	19
2014	19.235294117647058
2015	18.25
2016	17.58823529411765
2017	17.235294117647058
2018	16.705882352941178
2019	16.058823529411764