Year	Number of
1980	16410
1981	16690
1982	17290
1983	17300
1984	16360
1985	15990
1986	14680
1987	13370
1988	13270
1989	12640
1990	12310
1991	12180
1992	12610
1993	13890
1994	13680
1995	13450
1996	13400
1997	12620
1998	12280
1999	11870
2000	11770
2001	11460
2002	11550
2003	10730
2004	10620
2005	9770
2006	9406
2007	9755