Year	Number
1994	15.99612
1995	16.37765
1996	15.69779
1997	16.67526
1998	18.36871
1999	17.32988
2000	18.05492
2001	19.31847
2002	19.28928
2003	18.52009
2004	18.76095
2005	18.52723
2006	18.34212
2007	17.57316
2008	17.2241
2009	17.23933
2010	17.10394
2011	17.23898
2012	17.50147
2013	19.99801
2014	19.83449
2015	19.3665
2016	19.01932
2017	18.74768
2018	18.66079