Year	Number
1993	20.7308
1994	19.76084
1995	21.06175
1996	18.75483
1997	19.78897
1998	22.27169
1999	22.28839
2000	22.86479
2001	22.95129
2002	22.22184
2003	22.44697
2004	22.60178
2005	21.54186
2006	20.82627
2007	20.3175
2008	19.65107
2009	19.68
2010	18.95542
2011	19.51429
2012	20.50218
2013	25.3512
2014	25.83924
2015	25.23081
2016	24.52977
2017	24.24424
2018	23.96436