Year	Number of
1990	273.21
1991	277.14
1992	277.51
1993	277.59
1994	285.44
1995	299.22
1996	307.17
1997	316.68
1998	321.34
1999	325.63
2000	339.05
2001	349.56
2002	357.69
2003	362.04
2004	368.78
2005	374.35
2006	384.46
2007	395.29
2008	402.93
2009	410.9
2010	421.13
2011	431.13
2012	447.49
2013	457.37
2014	466.98
2015	479.99
2016	491.87