Year	Number of
1990	62.38
1991	63.15
1992	65.71
1993	68.74
1994	71.26
1995	72.45
1996	77.75
1997	81.37
1998	83.43
1999	86.9
2000	88.58
2001	90.39
2002	92.59
2003	95.21
2004	99.08
2005	100.9
2006	103.59
2007	107.77
2008	111.91
2009	116.05
2010	121.49
2011	126.29
2012	130.97
2013	134.67
2014	139.9
2015	145.58
2016	151.43