Year	Number
1976	43.11111
1977	43.23148
1978	41.80992
1979	41.96923
1980	36.19643
1981	35.14525
1983	30.90129
1984	32.57826
1995	21.50839
1998	18.50954
1999	22.5019
2000	21.99718
2001	20.22957
2002	21.18264
2003	22.32538
2006	16.49447
2007	17.04336
2008	15.46104
2009	17.34812
2011	18.9628
2012	18.49686
2013	20.71104
2014	21.84952
2015	22.09197
2016	22.95188
2017	22.91741
2018	21.09542