Year	Number
1975	23000
1976	26000
1977	27300
1978	28500
1979	28500
1980	30000
1981	30200
1982	34000
1983	26400
1984	56000
1985	58000
1986	59000
1987	28900
1988	43600
1989	29600
1990	30000
1992	16500
1993	17500
1994	14500
1995	14500
1996	15200
1997	0
1998	0
2000	19009
2001	13877
2002	13877
2003	13599
2004	15503
2005	16743
2006	18752
2007	20252
2008	21420
2009	21784
2010	0
2011	48789
2012	50193