Year	Number of
1990	15610
1991	15940
1992	16260
1993	16520
1994	16740
1995	16950
1996	17190
1997	17460
1998	17760
1999	18070
2000	18390
2001	18720
2002	19060
2003	19400
2004	19730
2005	20060
2006	20380
2007	20690