Year	Number
1988	14.27195
1989	14.29637
1990	13.94181
1991	13.35407
1992	13.06805
1993	12.57666
1994	12.48844
1995	12.36866
1996	12.1185
1997	12.04334
1998	12.0777
1999	12.14472
2000	12.11241
2001	12.3386
2002	12.35431
2003	12.62796
2004	11.99928
2005	11.46598
2006	11.28617
2007	11.19383
2008	11.12594
2009	10.85999
2010	10.70796
2011	10.16726
2012	9.96592
2013	10.41704
2014	10.39318
2015	10.14677
2016	10.0146
2017	9.9961
2018	10.02635