Year	Number
1992	15.15416
1993	15.00311
1994	15.12378
1995	15.38689
1996	15.34799
1997	15.00903
1998	15.16586
1999	15.10347
2000	15.04878
2001	14.95944
2002	14.62578
2003	14.61619
2004	14.49582
2005	14.39859
2006	14.31007
2007	14.16142
2008	14.06454
2009	13.97572
2010	13.89123
2011	14.0107
2012	14.18429
2013	14.48071
2014	14.35433
2015	14.19263
2016	14.00329
2017	13.99559
2018	14.0014