Year	1=extremely inefficient to 7=extremely efficient
2007	3.1830985915493
2008	3.50383821043911
2009	3.9965190975
2010	4.349567128
2011	4.5
2012	4.3
2013	4.1
2014	4.1
2015	4.0211406218939
2016	4
2017	4.2