Year	Number of
1990	20.78
1991	21.93
1992	23.46
1993	24.99
1994	25.98
1995	27.26
1996	28.44
1997	29.95
1998	30.28
1999	31.43
2000	32.3
2001	34.25
2002	35.69
2003	35.97
2004	36.27
2005	35.82
2006	37.34
2007	38.39
2008	39.36
2009	39.97
2010	40.82
2011	41.58
2012	42.55
2013	42.53
2014	43.7
2015	44.73
2016	46.2