Year	Number
1994	18.57689
1995	18.89777
1996	19.60983
1997	19.56411
1998	18.89542
1999	19.56128
2000	19.73738
2001	19.94034
2002	19.91493
2003	20.15125
2004	20.14728
2005	19.7307
2006	19.32217
2007	19.16871
2008	18.69327
2009	18.26717
2010	18.36429
2011	18.52106
2012	18.51585
2013	17.9827
2014	17.86439
2015	17.76367
2016	17.30158
2017	17.14844
2018	17.24682