Year	Number
1971	34.28763
1972	35.31724
1973	35.00678
1974	35.59747
1975	36.74045
1980	37.74511
1981	38.17194
1982	36.2732
1983	36.09122
1984	34.4961
1985	27.49637
1986	27.84867
1987	27.02589
1988	25.98072
1989	25.00526
1990	24.9825
1991	27.09087
1992	27.08407
1993	27.6281
1994	28.05102
1995	28.25967
1996	28.24294
1997	27.62886
1998	27.70111
1999	28.14105
2000	28.76272
2001	28.13457
2002	28.30725
2003	28.17638
2004	27.55149
2005	27.09953
2006	26.95752
2007	27.38468
2008	26.53204
2009	26.6096
2010	26.23715
2011	26.41532
2012	25.83553
2013	25.98351
2014	25.66659
2015	25.88159
2016	26.59118
2017	28.03417
2018	26.80065