Year	Number
1998	13.50234
1999	13.18487
2000	13.28184
2001	13.33299
2002	13.58167
2003	13.5953
2004	13.41248
2005	13.58803
2006	13.20529
2007	13.28329
2008	13.11523
2009	13.09159
2010	12.85133
2011	12.68348
2012	12.38423
2013	12.36151
2014	12.42319
2015	12.26166
2016	11.79789
2017	11.42552
2018	11.90226