Year	Number of
1990	167.33
1991	165.82
1992	164.54
1993	171.46
1994	189
1995	199.99
1996	213.68
1997	220.6
1998	219.07
1999	226.32
2000	226.28
2001	219.95
2002	217.31
2003	227.07
2004	236.36
2005	247.44
2006	253.68
2007	261.85
2008	269.59
2009	272.13
2010	279.23
2011	283.26
2012	289.03
2013	297.32
2014	305.49
2015	315.57
2016	324.61