Year	Number
1993	20.03788
1994	19.12464
1995	20.12455
1996	18.30407
1997	19.50057
1998	21.01927
1999	21.26132
2000	21.76293
2001	21.89182
2002	21.38235
2003	21.36716
2004	21.42447
2005	20.49021
2006	19.85909
2007	19.38495
2008	18.78436
2009	18.42951
2010	18.43067
2011	18.93396
2012	19.13572
2013	22.77111
2014	22.93721
2015	22.51799
2016	21.73447
2017	21.59494
2018	21.51149