Year	1=extremely inefficient to 7=extremely efficient
2007	4.31121037220549
2008	4.36939796443868
2009	4.42737912923636
2010	4.41639900145455
2011	4.3
2012	4.26363636363636
2013	4.38181818181818
2014	4.52727272727273
2015	4.52321265539673
2016	4.53636363636364
2017	4.60909090909091