Year	Number of
1990	148.36
1991	157.66
1992	167.13
1993	177.43
1994	189.87
1995	208.37
1996	220.47
1997	231.63
1998	250.49
1999	265.26
2000	279.58
2001	291.7
2002	298.85
2003	309.15
2004	317.24
2005	326.05
2006	334.27
2007	346.47
2008	360.22
2009	378.06
2010	394.17
2011	409.24
2012	421.14
2013	440.01
2014	456.42
2015	480.64
2016	506.37