Year	Number of
1990	20.17
1991	20.92
1992	21.75
1993	22.68
1994	23.68
1995	24.79
1996	25.91
1997	27.07
1998	28.69
1999	30.55
2000	32.33
2001	33.7
2002	36.45
2003	38.13
2004	39.14
2005	40.66
2006	43.93
2007	47.16
2008	51.18
2009	55.5
2010	60.64
2011	66.36
2012	70.81
2013	75.16
2014	80.83
2015	84.78
2016	89.11