Year	Number of
1990	261.7
1991	260.55
1992	259.25
1993	257.7
1994	256.24
1995	255.47
1996	250.41
1997	245.25
1998	240.17
1999	234.86
2000	229.66
2001	226.91
2002	224.2
2003	221.73
2004	219.8
2005	218.35
2006	220.63
2007	222.79
2008	225.21
2009	227.95
2010	231.16
2011	236.1
2012	241.27
2013	246.82
2014	253.1
2015	259.65
2016	266.53