Year	1=extremely inefficient to 7=extremely efficient
2007	3.15068493150685
2008	3.75120502174441
2009	4.5713315577
2010	4.704041296
2011	4.9
2012	5.2
2013	5.3
2014	5.6
2015	5.45561838626862
2016	5.5
2017	5.4