Year	Number of
1990	51.29
1991	52.32
1992	53.58
1993	55.06
1994	56.72
1995	58.55
1996	60.68
1997	63.08
1998	65.72
1999	68.53
2000	71.53
2001	74.75
2002	78.28
2003	82.13
2004	86.27
2005	90.76
2006	94.54
2007	98.59
2008	103.03
2009	107.87
2010	113.21
2011	118.18
2012	123.64
2013	129.41
2014	135.65
2015	142.41
2016	149.39