Year	Number
1992	12.5854
1993	12.52239
1994	12.73681
1995	13.16067
1996	13.17736
1997	13.0235
1998	12.89365
1999	12.82418
2000	12.51048
2001	12.23826
2002	12.21651
2003	12.18933
2004	12.04483
2005	11.85121
2006	11.73361
2007	11.42662
2008	11.23094
2009	11.30787
2010	11.33338
2011	11.40014
2012	11.57951
2013	11.7807
2014	11.61077
2015	11.5303
2016	11.24983
2017	11.30121
2018	11.30701