Year	years
2003	2.9916666666666667
2004	2.9657894736842105
2005	2.9452380952380954
2006	2.9465116279069767
2007	2.9250000000000003
2008	2.9250000000000003
2009	2.9044444444444446
2010	2.9044444444444446
2011	2.897777777777778
2012	2.9434782608695653
2013	2.9319148936170216
2014	2.9234042553191495
2015	2.912765957446809
2016	2.902127659574469
2017	2.902127659574469
2018	2.902127659574469
2019	2.885106382978724