Year	Number of
1990	154.12
1991	153.55
1992	155.16
1993	157.18
1994	159.4
1995	162.67
1996	166.15
1997	169.37
1998	173.38
1999	186.93
2000	201.22
2001	213.92
2002	227.45
2003	244.95
2004	263.83
2005	281.08
2006	301.58
2007	317.17
2008	330.53
2009	346.33
2010	365.67
2011	386.75
2012	410.71
2013	441.39
2014	471.16
2015	498.55
2016	533.93