Year	Number of
1990	263.6
1991	264.83
1992	266.5
1993	256.94
1994	255.77
1995	259.8
1996	261.29
1997	265.21
1998	260.3
1999	268.59
2000	281.71
2001	301.34
2002	317.89
2003	332.24
2004	344.82
2005	362
2006	377.28
2007	399.88
2008	420.13
2009	440.7
2010	462.3
2011	469.81
2012	475.43
2013	476.45
2014	478.27
2015	482.48
2016	488.68