Year	number
2003	11.2
2004	11.028571428571428
2005	11
2006	10.8
2007	10.6
2008	9.95
2009	9.475
2010	9.275
2011	8.65
2012	8.642857142857142
2013	8.534883720930232
2014	8.209302325581396
2015	8.090909090909092
2016	7.7727272727272725
2017	7.545454545454546
2018	7.409090909090909
2019	7.181818181818182