Year	Number
1971	8244
1972	9387
1973	11734
1974	14490
1975	17575
1976	19721
1977	20367
1978	21614
1979	20344
1980	19173
1981	19998
1982	20697
1983	22350
1984	24651
1985	25805
1986	28887
1987	30766
1988	32922
1989	36783
1992	42871
1995	56457
1996	72888
1997	77384
1999	80382
2001	94113
2002	97604
2011	146080