Year	Number of
1990	45.24
1991	46.99
1992	48.95
1993	51.05
1994	53.45
1995	56.19
1996	58.69
1997	61.3
1998	63.92
1999	66.51
2000	69.08
2001	72.29
2002	75.34
2003	78.74
2004	81.99
2005	85.32
2006	89.41
2007	93.92
2008	99.21
2009	105.31
2010	112.36
2011	119.4
2012	127.14
2013	135.03
2014	143.48
2015	152.61
2016	163.36