Year	1=extremely inefficient to 7=extremely efficient
2007	3.6158940397351
2008	3.6555997866536
2009	3.9101799195
2010	4.0381614287
2011	3.8
2012	3.8
2013	3.8
2014	3.9
2015	4.26472408851521
2016	4.3
2017	4.6