Year	Number
1970	7.27655
1971	7.36992
1972	7.51869
1973	7.58144
1974	7.70343
1975	7.67988
1976	7.56055
1977	7.4151
1978	7.47264
1979	7.25784
1983	7.57642
1984	7.64464
1985	7.82314
1986	7.76125
1987	7.15971
1988	7.09614
1994	9.66461
1998	12.41851
2000	12.30048
2001	17.48206
2002	17.04147
2003	16.14991
2004	15.42813
2005	15.1209
2006	14.19154
2007	13.63714
2008	12.23531