Year	Number
1970	9175
1971	10295
1972	10692
1973	11700
1974	12138
1975	14134
1976	14789
1977	14760
1978	16073
1979	17513
1980	20701
1981	21719
1982	20604
1983	23323
1984	22128
1985	20560
1986	21227
1987	22484
1988	23248
1999	9603
2000	9039
2001	12754
2002	14664
2003	14106
2004	17160
2005	18754
2006	22952
2007	25017
2008	29697
2009	15672