Year	Number of
1990	466.91
1991	474.83
1992	479.14
1993	488.68
1994	501.87
1995	521.3
1996	533.05
1997	544.6
1998	548.08
1999	548.68
2000	548.4
2001	548.78
2002	555.29
2003	553.15
2004	543.78
2005	539.03
2006	538.51
2007	536.24
2008	536.85
2009	538.02
2010	547.58
2011	544.76
2012	544.55
2013	550.75
2014	557.42
2015	560.31
2016	580.51