Year	number
2004	7.111111111111111
2005	6.947368421052632
2006	6.9
2007	6.85
2008	6.2
2009	5.904761904761905
2010	5.904761904761905
2011	5.857142857142857
2012	5.857142857142857
2013	5.590909090909091
2014	5.454545454545454
2015	5.2727272727272725
2016	5.2272727272727275
2017	5.181818181818182
2018	5.181818181818182
2019	5.2727272727272725