Year	1=extremely inefficient to 7=extremely efficient
2007	4.21195652173913
2008	4.45608974492961
2009	4.5691818239
2010	4.5343630946
2011	4.4
2012	4.2
2013	4.2
2014	4.3
2015	4.21926270674083
2016	4.2
2017	4.6