Year	Number of
1990	137.24
1991	138.32
1992	139.69
1993	142.71
1994	144.22
1995	146.26
1996	147.15
1997	149.87
1998	153.8
1999	153.9
2000	157.09
2001	154
2002	152.95
2003	153.76
2004	155.12
2005	156.97
2006	160.98
2007	166.05
2008	170.99
2009	176.08
2010	184.97
2011	191.55
2012	201.21
2013	210.95
2014	219.46
2015	228.15
2016	237.62