Year	Number
1971	4008
1972	5194
1973	5884
1974	5782
1975	7551
1976	12148
1977	15927
1978	18610
1979	22384
1980	26872
1981	31940
1982	39266
1983	45235
1984	51277
1985	56126
1986	61478
1987	67621
1988	75813
1989	84866
1990	94979
1991	107115
1992	117118
1993	128643
1994	144000
1995	158625
1997	178839
1998	188313
2016	433144
2017	520274