Year	1=extremely inefficient to 7=extremely efficient
2007	4.3804347826087
2008	4.18016236637228
2009	4.115600852
2010	4.3160840208
2011	4.4
2012	4.5
2013	4.3
2014	4.3
2015	4.21691146918706
2016	4.2
2017	4.5