Year	1=extremely inefficient to 7=extremely efficient
2007	3.36
2008	3.51726302122905
2009	3.6279788627
2010	3.483039114
2011	3.5
2012	3.6
2013	3.9
2014	4.1
2015	3.80427816708883
2016	3.8
2017	3.9