Year	Number of
1990	57.63
1991	57.65
1992	59.29
1993	60.98
1994	61.4
1995	62.22
1996	64.01
1997	65.7
1998	67.91
1999	70.54
2000	72.8
2001	75.3
2002	78.3
2003	82.21
2004	86.11
2005	90.01
2006	93.88
2007	98.74
2008	103.77
2009	108.83
2010	115.35
2011	119.47
2012	123.62
2013	128
2014	132.95
2015	138.35
2016	143.93