Year	Number of
1990	217.51
1991	224.46
1992	232.36
1993	241.06
1994	250.5
1995	260.8
1996	266.86
1997	273.86
1998	281.56
1999	289.95
2000	299.12
2001	307.16
2002	316.3
2003	326.27
2004	336.94
2005	348.32
2006	359.03
2007	370.48
2008	383.02
2009	396.55
2010	411.24
2011	426.22
2012	442.63
2013	460.25
2014	479.05
2015	499.02
2016	518.81