Year	Number of
1990	20.27
1991	20.54
1992	20.59
1993	20.46
1994	20.3
1995	21.96
1996	24.29
1997	26.61
1998	27.37
1999	28.01
2000	26.14
2001	28.15
2002	29.94
2003	29.74
2004	30.44
2005	32.74
2006	33.59
2007	33.52
2008	34.41
2009	35.53
2010	36.31
2011	36.59
2012	38.22
2013	39.12
2014	39.45
2015	43.44
2016	47.31