Year	Number
1970	19651
1971	20273
1972	20024
1973	19313
1974	19766
1975	19337
1976	19475
1977	19434
1978	20111
1979	20377
1981	18504
1982	18992
1983	20677
1984	20734
1985	20463
1986	21859
1987	22550
1988	23475
1989	25334
1990	24457
1991	24798
1992	24653
1993	26694
1994	27474
1995	27086
1996	30278
2009	27494
2010	21536
2011	18342
2012	20962
2013	25503
2014	24926
2015	26225