Year	Number
1971	1699
1972	1871
1973	1950
1975	1629
1976	2596
1977	2652
1978	2855
1984	4520
1985	4927
1986	3006
1988	5820
1989	5130
1990	5451
1991	5969
2001	5840
2011	17194
2012	18482
2013	20196
2015	21874
2016	22129