Year	1=extremely inefficient to 7=extremely efficient
2007	2.73972602739726
2008	2.89975322110445
2009	3.0336731844
2010	2.9969243268
2011	2.9
2012	2.6
2013	2.7
2014	2.9
2015	2.90646923192471
2016	2.9
2017	3.3