Year	Number of
1990	31.18
1991	31.89
1992	32.69
1993	33.74
1994	35.16
1995	35.78
1996	35.65
1997	36.95
1998	38.73
1999	40.16
2000	41.06
2001	42.32
2002	42.48
2003	42.46
2004	42.73
2005	43.84
2006	46.39
2007	48.81
2008	50.38
2009	51.05
2010	52.53
2011	53.39
2012	54.74
2013	56.02
2014	57.21
2015	58.32
2016	60.21