Year	Number of
1990	153.79
1991	158.08
1992	162.84
1993	168.11
1994	173.63
1995	179.39
1996	180.59
1997	181.96
1998	183.25
1999	184.99
2000	187.36
2001	188.65
2002	190.33
2003	192.18
2004	194.58
2005	197.62
2006	200.88
2007	204.49
2008	208.49
2009	213.06
2010	218.31
2011	222.32
2012	226.79
2013	231.06
2014	235.96
2015	241.56
2016	249.2