Year	Number of
1990	21.5
1991	23.26
1992	25.51
1993	28.07
1994	31.02
1995	34.24
1996	34.08
1997	33.48
1998	32.66
1999	32.11
2000	31.6
2001	33.07
2002	34.91
2003	36.69
2004	38.27
2005	40.15
2006	42.05
2007	43.81
2008	47.85
2009	54.55
2010	62.99
2011	69.78
2012	79.38
2013	92.34
2014	107.3
2015	124.49
2016	145.39