Year	Number
1999	16.86515
2000	17.3742
2001	16.84448
2002	17.06113
2004	16.46241
2005	16.32756
2006	16.51494
2007	16.26539
2008	16.41088
2009	16.01972
2010	16.87022
2011	16.09007
2012	15.66517
2013	16.62432
2014	15.26292
2015	14.19656
2016	14.56216
2017	14.66029