Year	Number of
1990	50.65
1991	53.24
1992	55.82
1993	58.23
1994	61.01
1995	63.71
1996	66.12
1997	68.17
1998	70.26
1999	71.51
2000	72.64
2001	73.85
2002	75.1
2003	77.25
2004	78.92
2005	81.33
2006	83.84
2007	86.23
2008	89.65
2009	93.29
2010	96.73
2011	101.35
2012	105.86
2013	110.92
2014	116.02
2015	121.95
2016	128.8