Year	Number of
1990	590.58
1991	599.72
1992	599.51
1993	591.18
1994	585.6
1995	581.01
1996	576.02
1997	572.4
1998	568.23
1999	563.23
2000	569.02
2001	572.91
2002	580.46
2003	588.52
2004	587.42
2005	573.83
2006	560.9
2007	558.95
2008	564.89
2009	566.57
2010	564.09
2011	566.45
2012	569.43
2013	573.07
2014	581.65
2015	579.86
2016	583.54