Year	number
2005	23.791666666666668
2006	23.52
2007	23.6
2008	22.2
2009	22.08
2010	22.08
2011	22.52
2012	23.615384615384617
2013	23.724137931034484
2014	23.75862068965517
2015	23.137931034482758
2016	21.379310344827587
2017	20.448275862068964
2018	19.93103448275862
2019	19.482758620689655