Year	Number of
1990	26.67
1991	27.59
1992	28.52
1993	29.56
1994	30.64
1995	31.88
1996	33.1
1997	34.5
1998	36.08
1999	37.71
2000	39.53
2001	41.39
2002	43.41
2003	45.37
2004	47.35
2005	49.35
2006	50.91
2007	52.41
2008	53.86
2009	55.42
2010	56.98
2011	58.55
2012	60.13
2013	61.6
2014	63.09
2015	64.49
2016	65.38