Year	years
2003	2.963829787234042
2004	2.9374999999999996
2005	2.990566037735849
2006	2.9370370370370362
2007	2.912962962962963
2008	2.912962962962963
2009	2.912962962962963
2010	2.8685185185185187
2011	2.758181818181818
2012	2.734545454545454
2013	2.636065573770492
2014	2.6278688524590166
2015	2.6475409836065573
2016	2.6180327868852458
2017	2.6065573770491803
2018	2.6065573770491803
2019	2.5622950819672132