Year	Number of
1990	13.95
1991	15.05
1992	16.25
1993	17.58
1994	19.02
1995	20.6
1996	22.47
1997	24.49
1998	26.73
1999	29.13
2000	31.71
2001	33.27
2002	34.87
2003	36.51
2004	38.29
2005	40.25
2006	41.67
2007	43.21
2008	44.89
2009	46.64
2010	48.49
2011	50.84
2012	53.32
2013	55.96
2014	58.75
2015	61.71
2016	64.82