Year	1=extremely inefficient to 7=extremely efficient
2007	3.01351351351351
2008	3.26129848329084
2009	3.6973797069
2010	3.8633159284
2011	3.9
2012	4
2013	4
2014	4
2015	3.89725387172496
2016	3.9
2017	4.2