Year	Number of
1990	450.7
1991	436.43
1992	442.42
1993	443.32
1994	451.27
1995	444.9
1996	441.96
1997	443.64
1998	450.88
1999	458.79
2000	463.6
2001	465.13
2002	475.17
2003	503.25
2004	511.51
2005	513.58
2006	506.64
2007	508.07
2008	534.58
2009	540.18
2010	540.5
2011	518.12
2012	540.46
2013	499.09
2014	491.48
2015	493.65
2016	493.29