Year	Number of
1990	79.61
1991	81.93
1992	84.54
1993	87.32
1994	90.32
1995	93.61
1996	96.32
1997	99.18
1998	102.12
1999	105.37
2000	108.95
2001	112.4
2002	115.97
2003	120.2
2004	124.54
2005	129.16
2006	134.22
2007	139.43
2008	144.99
2009	150.32
2010	155.67
2011	158.9
2012	163.18
2013	165.96
2014	169.2
2015	173.01
2016	177.09