Year	1=extremely inefficient to 7=extremely efficient
2007	3.1495833966409
2008	3.1847524821625
2009	3.4157744336
2010	3.72769131802
2011	3.72
2012	3.7
2013	3.76666666666667
2014	3.8
2015	3.77533075630101
2016	3.8
2017	3.95