Year	Number of
1990	174.45
1991	178.69
1992	181.4
1993	180.05
1994	180.15
1995	182.25
1996	185.01
1997	189.18
1998	197.19
1999	206.92
2000	219.36
2001	234
2002	251.46
2003	276.62
2004	299.4
2005	319.55
2006	336.36
2007	350.27
2008	364.6
2009	378.27
2010	393.22
2011	406.76
2012	423.36
2013	439.5
2014	456.73
2015	465.4
2016	477.9