Year	Number
2002	20.46514
2003	20.59161
2004	21.88809
2005	21.225
2006	20.63908
2007	20.39706
2008	19.90326
2009	20.06177
2010	21.01884
2011	18.95689
2012	19.67879
2013	17.38283
2014	17.00185
2015	16.86045
2016	17.04332
2017	16.32339
2018	16.70423