Year	Number of
1990	306.62
1991	311.8
1992	324.38
1993	334.68
1994	338.91
1995	341.65
1996	353.24
1997	360.83
1998	362.72
1999	368.29
2000	377.12
2001	385.54
2002	401.09
2003	407.78
2004	410.92
2005	409.78
2006	418.51
2007	419.62
2008	422.46
2009	427.85
2010	435.51
2011	449.66
2012	466.1
2013	491.89
2014	513.32
2015	523.99
2016	538.49