Year	1=extremely inefficient to 7=extremely efficient
2007	5.5
2008	5.61985755408163
2009	5.8811285056
2010	5.8285719778
2011	5.8
2012	6
2013	5.9
2014	5.9
2015	5.87797459898324
2016	5.9
2017	5.8