Year	Number of
1990	231.26
1991	230.5
1992	230.28
1993	230.28
1994	230.03
1995	230.53
1996	230.43
1997	230.11
1998	230.08
1999	229.46
2000	229.72
2001	233.81
2002	237.52
2003	241.19
2004	245.01
2005	249.09
2006	254.72
2007	260.27
2008	266.14
2009	272.26
2010	278.99
2011	283.64
2012	287.54
2013	292
2014	296.46
2015	300.93
2016	305.62