Year	Number of
1990	137.62
1991	138.24
1992	134.75
1993	131.99
1994	132.33
1995	131.83
1996	133.22
1997	135.73
1998	138.94
1999	142.22
2000	146.91
2001	152.32
2002	158.8
2003	164.91
2004	171.36
2005	177.74
2006	182.86
2007	188.3
2008	194.12
2009	199.43
2010	206.4
2011	212.84
2012	221.2
2013	230.1
2014	239.68
2015	250.36
2016	259.91