Year	1=extremely inefficient to 7=extremely efficient
2007	3.22673179819226
2008	3.22858540646956
2009	3.50621263476429
2010	3.66802711198387
2011	3.6125
2012	3.59
2013	3.54
2014	3.51428571428571
2015	3.52208006149083
2016	3.52727272727273
2017	3.55