Year	years
2003	3.001111111111111
2004	2.9763440860215056
2005	2.974528301886793
2006	2.9481481481481486
2007	2.9275229357798174
2008	2.9275229357798174
2009	2.91909090909091
2010	2.897272727272728
2011	2.8396396396396395
2012	2.8294642857142853
2013	2.7595041322314047
2014	2.752066115702479
2015	2.7578512396694213
2016	2.7388429752066124
2017	2.73305785123967
2018	2.7330578512396695
2019	2.7041322314049596