Year	1=extremely inefficient to 7=extremely efficient
2007	2.50381679389313
2008	2.48635390668859
2009	2.8891364665
2010	3.3091823656
2011	3.1
2012	3.1
2013	3
2014	2.7
2015	2.93577572908432
2016	2.9
2017	3