Year	1=extremely inefficient to 7=extremely efficient
2007	5.175
2008	5.02939232871287
2009	5.1239327438
2010	5.166273619
2011	5.2
2012	5.3
2013	5.4
2014	5.5
2015	5.66235354072169
2016	5.7
2017	5.4