Year	Number of
1990	63.57
1991	65.12
1992	66.99
1993	69.46
1994	71.38
1995	73.61
1996	75.68
1997	78.08
1998	80.51
1999	82.33
2000	84.63
2001	86.93
2002	89.7
2003	92.88
2004	96.12
2005	99.15
2006	102.28
2007	105.74
2008	109.88
2009	114.55
2010	119.59
2011	124.93
2012	130.59
2013	136.54
2014	143.01
2015	150.2
2016	157.68