Year	Number
2009	1.71611428260803
2010	1.72867774963379
2011	1.73314356803894
2012	1.71242761611938
2013	1.68905031681061
2014	1.7343989610672
2015	1.67126309871674
2016	1.68995451927185
2017	1.68861532211304
2018	1.70172333717346
2019	1.71052813529968
2020	1.70157599449158
2021	1.68722951412201
2022	1.69060826301575