Year	Number of
1990	112.68
1991	116.97
1992	120.85
1993	129.69
1994	135.42
1995	144.22
1996	149.33
1997	152.64
1998	157.4
1999	162.67
2000	167.12
2001	171.6
2002	171.51
2003	173.99
2004	173.44
2005	177.22
2006	181.89
2007	183.73
2008	186.75
2009	189.78
2010	195.74
2011	203.68
2012	211.54
2013	218.85
2014	225.4
2015	231.77
2016	239.69