Year	1=extremely inefficient to 7=extremely efficient
2007	3.27445585315149
2008	3.33694769750925
2009	3.52686297963889
2010	3.66403478336842
2011	3.64736842105263
2012	3.67368421052631
2013	3.77222222222222
2014	3.88888888888889
2015	3.89595974697722
2016	3.88947368421053
2017	4.02222222222222