Year	Number
1992	13.79505
1994	12.04122
1999	13.06712
2000	12.41715
2001	12.41712
2002	12.65773
2003	12.92597
2004	13.17341
2005	13.89993
2006	14.26095
2007	14.31912
2008	14.20058
2009	14.04529
2010	13.0902
2011	12.7783
2012	12.08223
2013	11.28811
2014	11.01798
2015	10.53581
2016	10.37309
2017	10.43823
2018	10.32792