Year	Number of
1990	12.57
1991	13.65
1992	14.98
1993	16.45
1994	18.18
1995	20.21
1996	23.04
1997	26.33
1998	30.16
1999	34.74
2000	40.21
2001	42.08
2002	44.2
2003	46.89
2004	49.57
2005	52.17
2006	54.05
2007	55.84
2008	58.23
2009	60.73
2010	63.3
2011	63.89
2012	64.57
2013	65.03
2014	65.72
2015	66.71
2016	68.31