Year	Number of
1990	139.35
1991	141.21
1992	145.75
1993	150.27
1994	154.92
1995	158.03
1996	165.74
1997	166.02
1998	167.73
1999	174.49
2000	177.42
2001	180.33
2002	181.97
2003	186.06
2004	187.2
2005	190.57
2006	190.55
2007	192.81
2008	195.18
2009	199.39
2010	207.49
2011	216.54
2012	223.56
2013	229.69
2014	235.2
2015	244.52
2016	253.67