Year	Number of
1990	153.69
1991	157.58
1992	161.86
1993	166.47
1994	171.49
1995	177.08
1996	180
1997	183.45
1998	187.43
1999	191.95
2000	197.18
2001	198.98
2002	201.46
2003	204.34
2004	207.39
2005	210.67
2006	215.43
2007	220.15
2008	225.34
2009	231.02
2010	237.52
2011	241.58
2012	246.4
2013	251.72
2014	257.59
2015	263.99
2016	270.27