Year	number
2005	22
2006	20.56
2007	19.68
2008	19.03846153846154
2009	18.576923076923077
2010	18.192307692307693
2011	17.62962962962963
2012	13.62962962962963
2013	12.74074074074074
2014	11.74074074074074
2015	10.851851851851851
2016	10.777777777777779
2017	10.814814814814815
2018	10.703703703703704
2019	10.296296296296296