Year	number
2005	44.35
2006	41.6
2007	41.55
2008	36.35
2009	35.05
2010	35.05
2011	32.05
2012	29.85
2013	26.936818181818182
2014	26.66409090909091
2015	26.07318181818182
2016	24.98227272727273
2017	23.527727272727272
2018	23.345909090909092
2019	23.300454545454546