Year	1=extremely inefficient to 7=extremely efficient
2007	5.28571428571429
2008	5.18127062461274
2009	5.2075142389
2010	5.2073189633
2011	5.2
2012	5.4
2013	5.5
2014	5.6
2015	5.50814908568622
2016	5.5
2017	5.8