Year	Number of
1990	58.1
1991	59.03
1992	59
1993	59.87
1994	59.42
1995	60.34
1996	61.96
1997	62.85
1998	65.97
1999	69.74
2000	71.61
2001	73.93
2002	76.04
2003	78.04
2004	81.84
2005	86.68
2006	89.97
2007	93.83
2008	98.43
2009	104.39
2010	110.82
2011	115.89
2012	120.33
2013	125.57
2014	126.25
2015	128.63
2016	131.27