Year	Number of
1990	14.73
1991	15.37
1992	16.09
1993	16.88
1994	17.72
1995	18.6
1996	19.39
1997	20.23
1998	21.12
1999	22.05
2000	23.04
2001	24.55
2002	26.17
2003	27.92
2004	29.89
2005	32.12
2006	33.88
2007	35.82
2008	38.01
2009	40.36
2010	42.86
2011	45.14
2012	47.52
2013	50
2014	52.56
2015	55.24
2016	58.17