Year	Number of
1990	35.47
1991	36.29
1992	37
1993	37.46
1994	37.84
1995	38.26
1996	38.55
1997	39.16
1998	39.71
1999	40.07
2000	40.52
2001	41.35
2002	42.23
2003	43.01
2004	43.8
2005	44.71
2006	46.02
2007	47.44
2008	48.93
2009	50.56
2010	52.33
2011	54.11
2012	56.15
2013	58.2
2014	60.53
2015	62.98
2016	65.6