Year	Number of
1990	371.5
1991	365.54
1992	360.83
1993	355.24
1994	357
1995	357.26
1996	356.22
1997	357.13
1998	363.66
1999	372.75
2000	384.83
2001	387.82
2002	394.96
2003	407.8
2004	405.14
2005	412.3
2006	414.64
2007	420.37
2008	431.4
2009	436.98
2010	435.03
2011	440.09
2012	447.58
2013	455.48
2014	462.78
2015	468.41
2016	478.34