Year	Number
1971	7.04687
1972	7.48555
1973	5.58025
1974	7.72515
1975	7.07097
1976	6.09524
1977	6.37917
1978	5.82845
1979	5.0124
1980	4.94286
1981	4.69271
1982	5.29143
1983	3.49254
1984	4.20106
1985	4.91949
1986	4.33725
1987	4.70118
1988	5.86704
1989	5.70419
1990	8.41787
1991	7.6654
1994	10.60694
1995	12.9557
2010	30.38818