Year	Number
1992	13.63002
1993	13.4558
1994	13.38167
1995	13.12357
1996	13.06027
1997	13.03714
1998	13.33708
1999	13.33747
2000	13.00069
2001	13.03961
2002	13.13523
2003	13.0992
2004	12.95161
2005	12.85225
2006	12.85839
2007	12.72695
2008	12.77223
2009	12.54917
2010	12.52068
2011	12.45478
2012	12.39345
2013	12.66055
2014	12.76192
2015	12.70256
2016	12.58938
2017	12.51405
2018	12.56182