Year	Number
1978	32.91781
1979	32.35802
1980	31.18085
1982	42.14423
1983	31.58125
1984	27.60317
1985	32.83415
1986	29.83529
1987	27.92542
1988	27.35016
1989	30.18121
1991	26.32558
1992	26.25581
1993	27.3619
1994	25.87931
1995	24.91634
1996	27.34298
1998	23.89161
1999	21.30909
2000	20.94364
2001	21.14047
2002	21.18046
2003	20.88432
2005	14.70264
2006	15.94626
2008	15.74856
2009	15.9
2010	15.51218
2011	15.65318
2012	15.02748
2013	14.61631
2014	15.21667
2015	14.98916
2016	14.32013
2017	13.76516
2018	14.40441