Year	Number of
1990	267.86
1991	272.11
1992	270.54
1993	267.02
1994	265.08
1995	265.29
1996	271.39
1997	280.08
1998	291.47
1999	303.25
2000	314.67
2001	325.12
2002	336.74
2003	350.69
2004	363.06
2005	374.21
2006	389.08
2007	403.43
2008	417.63
2009	431.88
2010	447.03
2011	451.19
2012	459.62
2013	468.23
2014	478.45
2015	480.41
2016	481.99