Year	Number of
1990	521.25
1991	511.05
1992	500.46
1993	491.51
1994	483.97
1995	476.42
1996	471.57
1997	466.46
1998	460.91
1999	455.85
2000	451.02
2001	457.31
2002	464.11
2003	471.21
2004	478.61
2005	486.36
2006	485.86
2007	485.27
2008	485.29
2009	486.05
2010	487.11
2011	491.89
2012	497.02
2013	502.32
2014	507.78
2015	513.41
2016	519.4