Year	Number of
1990	454.97
1991	454.6
1992	458.12
1993	456.25
1994	451.64
1995	449.75
1996	445.35
1997	443.65
1998	442.15
1999	434.62
2000	431.99
2001	428.38
2002	432.08
2003	434.73
2004	431.39
2005	426.77
2006	430.21
2007	430.41
2008	431.8
2009	434.5
2010	438.44
2011	442.86
2012	471.4
2013	489.07
2014	508.79
2015	528.55
2016	546.51