Year	1=extremely inefficient to 7=extremely efficient
2007	2.28421052631579
2008	2.35260753983763
2009	2.7654042852
2010	3.3597673
2011	3.4
2012	3.2
2013	3.4
2014	3.5
2015	3.20049818140088
2016	3.2
2017	3.6