Year	Number
1971	37.80389
1972	36.11195
1973	33.12517
1974	34.02891
1975	33.55384
1976	31.94539
1977	30.16475
1978	29.62344
1979	29.7868
1981	26.62431
1982	27.53688
1983	28.55453
1984	31.10382
1985	31.14897
1986	31.19571
1987	30.91192
1988	31.14063
1989	30.62648
1990	30.48036
1991	30.38145
1992	29.27687
1993	28.4562
1994	27.42823
1995	27.74516
2012	20.13204
2013	19.83354
2014	19.32755
2015	18.40513
2017	16.97782