Year	Number of
1990	217.8
1991	223.58
1992	230.24
1993	237.36
1994	242.23
1995	247.02
1996	249.56
1997	254.49
1998	257.44
1999	262.94
2000	267.26
2001	272.43
2002	283.99
2003	293.84
2004	308.57
2005	325.07
2006	339.01
2007	357.55
2008	372.52
2009	385.53
2010	397.58
2011	408.71
2012	421.38
2013	435.39
2014	451.79
2015	468.77
2016	484.44