Year	Number of
1990	14.86
1991	15.65
1992	16.39
1993	17.1
1994	17.91
1995	18.72
1996	19.56
1997	20.38
1998	21.13
1999	21.63
2000	22.12
2001	22.62
2002	23.28
2003	24.19
2004	25.22
2005	26.22
2006	27.23
2007	28.56
2008	29.92
2009	31.13
2010	32.34
2011	33.53
2012	34.89
2013	36.34
2014	37.8
2015	39.26
2016	40.41