Year	1=extremely inefficient to 7=extremely efficient
2007	2.70588235294118
2008	2.60360398516843
2009	2.7416867574
2010	3.1589399923
2011	2.8
2012	2.5
2013	2.7
2014	2.8
2015	3.2422683388458
2016	3.2
2017	3.4