Year	Number of
1990	20.64
1991	21.25
1992	21.88
1993	22.66
1994	23.57
1995	24.7
1996	25.98
1997	27.69
1998	28.5
1999	30.01
2000	32.33
2001	34.55
2002	37.79
2003	40.98
2004	43.24
2005	45.4
2006	47.18
2007	48.83
2008	52.05
2009	55.43
2010	59.16
2011	63.02
2012	66.23
2013	69.68
2014	75.04
2015	78.68
2016	82.62