Year	Number
1994	21.94736
1995	22.03179
1996	22.01615
1997	22.09477
1998	22.39404
1999	22.61618
2000	22.19432
2001	21.82937
2002	21.74087
2003	20.65999
2004	19.62149
2005	19.15515
2006	18.92052
2007	18.6856
2008	18.64177
2009	18.13019
2010	17.74192
2011	17.47898
2012	17.51941
2013	17.03415
2014	17.14254
2015	17.75644
2016	18.50634
2017	18.17364
2018	18.08589