Year	Number of
1990	19.13
1991	19.84
1992	20.67
1993	21.6
1994	22.61
1995	23.74
1996	24.83
1997	25.97
1998	27.8
1999	29.71
2000	31.61
2001	33.15
2002	35.95
2003	37.72
2004	38.98
2005	40.64
2006	43.88
2007	47.06
2008	50.99
2009	55.01
2010	59.67
2011	65
2012	69.21
2013	73.13
2014	78.1
2015	81.56
2016	85.44