Year	Number of
1990	38.7
1991	40.54
1992	42.57
1993	44.87
1994	47.48
1995	50.17
1996	52.85
1997	55.58
1998	58.72
1999	61.88
2000	65.1
2001	68.17
2002	71.1
2003	73.33
2004	75.96
2005	78.69
2006	81.85
2007	85.23
2008	89.34
2009	93.18
2010	96.98
2011	100.57
2012	104.65
2013	108.99
2014	113.18
2015	117.82
2016	123.82