Year	Number of
1987	17660
1988	17980
1989	18050
1990	17780
1991	17240
1992	16400
1993	15530
1994	14970
1995	15000
1996	14740
1997	14990
1998	15520
1999	15970
2000	16230
2001	16190
2002	15980
2003	15770
2004	15640
2005	15610
2006	15620
2007	15790
2008	16000
2009	16240
2010	16460
2011	16650
2012	16840
2013	17000
2014	17040
2015	17030