Year	Number of
1990	54.37
1991	55.06
1992	54.35
1993	53.93
1994	54.77
1995	55.32
1996	56.59
1997	58.25
1998	60.37
1999	62.65
2000	65.29
2001	68.06
2002	71.28
2003	74.5
2004	77.81
2005	81.04
2006	83.77
2007	86.51
2008	89.28
2009	91.81
2010	94.84
2011	97.54
2012	100.84
2013	104.26
2014	107.82
2015	111.77
2016	115.99