Year	1=extremely inefficient to 7=extremely efficient
2007	5.2972972972973
2008	5.30171638378378
2009	5.183248048
2010	5.1787241987
2011	5.2
2012	5
2013	5.1
2014	5.2
2015	5.26372795180669
2016	5.3
2017	5.2