Year	Number
1974	20760
1975	20856
1976	18913
1977	19146
1978	19260
1979	19430
1980	19705
1981	19878
1982	20402
1983	21060
1984	20501
1985	20927
1986	20611
1987	20690
1988	20475
1989	20094
1990	20123
1991	20830
1992	21371
1993	22960
1994	25617
1995	26317
1996	26523
1997	27273
2021	30985