Year	Number
1971	8.80426
1972	8.76408
1973	7.66732
1974	14.91705
1978	22.7395
1979	20.18882
1980	13.77788
1981	13.67079
1982	13.17942
1983	12.70055
1984	11.08575
1986	20.80518
1987	22.22958
1988	20.96989
1989	18.3661
1990	19.50262
1991	20.16331
1994	13.09255
1995	16.8668
1999	23.47621
2000	27.12535
2001	27.05167
2002	30.73619
2003	35.02699
2004	35.83406
2005	39.44956
2009	34.06085
2014	31.22114