Year	Number
1974	30.66968
1975	30.33996
1976	30.75608
1977	29.88763
1978	28.16485
1979	27.29006
1980	28.49105
1981	30.11206
1982	29.68792
1983	29.44652
1984	28.65872
1985	27.64036
1986	23.23974
1987	23.80659
1988	23.91446
1989	25.91443
1990	27.09356
1991	29.05957
1992	27.765
1993	30.21381
1994	30.89085
1995	29.98269
1996	32.78334
1997	32.70742
1999	29.59855
2000	33.78522
2001	32.5811
2002	32.10887
2003	30.98782
2004	32.34112
2005	32.81364
2006	35.38932
2007	31.98986
2008	32.24014
2009	33.11177
2011	31.04223
2012	32.98357
2013	31.68167
2014	30.07899
2015	31.25587
2016	30.5794
2017	27.29644
2018	27.24556
2019	26.99486