Year	Number of
1990	37.56
1991	39.64
1992	42.02
1993	44.8
1994	47.9
1995	51.24
1996	54.68
1997	57.3
1998	60.13
1999	63.2
2000	65.83
2001	69.8
2002	74.1
2003	77.9
2004	83.42
2005	92.14
2006	99.04
2007	111.52
2008	125.93
2009	140.97
2010	156.26
2011	174.19
2012	190.94
2013	207.11
2014	223.64
2015	241.34
2016	256.96