Year	Number
1994	18.62105
1995	18.93444
1996	19.6074
1997	19.57289
1998	18.95385
1999	19.62994
2000	19.80623
2001	20.05694
2002	20.05833
2003	20.30596
2004	20.32708
2005	19.96823
2006	19.60734
2007	19.46879
2008	19.06416
2009	18.67273
2010	18.77138
2011	18.88683
2012	18.94338
2013	18.40341
2014	18.29076
2015	18.17001
2016	17.74531
2017	17.58627
2018	17.71122