Year	Number of
1990	443.78
1991	442.84
1992	445.99
1993	444.33
1994	438.84
1995	436.17
1996	430.91
1997	428.59
1998	426.81
1999	419.56
2000	417.21
2001	414.7
2002	419.22
2003	422.76
2004	420.83
2005	416.79
2006	419.49
2007	418.87
2008	419.12
2009	420.46
2010	422.44
2011	426.18
2012	452.81
2013	467.95
2014	484.24
2015	501.18
2016	516.48