Year	Number of
1990	66.23
1991	68.3
1992	70.59
1993	72.52
1994	74.75
1995	77.81
1996	81.37
1997	80.81
1998	83.57
1999	84.69
2000	87.26
2001	91.31
2002	94.55
2003	98.5
2004	102.68
2005	104.62
2006	108.27
2007	112.82
2008	117.75
2009	123.8
2010	129.05
2011	136.96
2012	144
2013	151.08
2014	157.99
2015	159.08
2016	161.04