Year	number
2003	13.076923076923077
2004	12.4375
2005	12
2006	12
2007	11.2
2008	10.3
2009	10.05
2010	10.15
2011	10
2012	9.857142857142858
2013	9.619047619047619
2014	9.428571428571429
2015	9.272727272727273
2016	9.045454545454545
2017	8.5
2018	7.863636363636363
2019	7.181818181818182