Year	Number
1994	18.41384
1995	17.98455
1996	17.75205
1997	17.85917
1998	18.36012
1999	18.82215
2000	18.81129
2001	18.74495
2002	18.93754
2003	18.29154
2004	18.25465
2005	17.89669
2006	17.56229
2007	17.14103
2008	16.84326
2009	16.70191
2010	16.33201
2011	16.10905
2012	16.11684
2013	15.99027
2014	16.1268
2015	16.22269
2016	16.52308
2017	16.1954
2018	16.02797