Year	Number of
1990	13.29
1991	13.68
1992	14.11
1993	14.62
1994	15.21
1995	15.75
1996	16.41
1997	17.32
1998	18.1
1999	19.17
2000	19.62
2001	20.57
2002	21.48
2003	22.4
2004	23.32
2005	24.31
2006	25.39
2007	26.67
2008	27.83
2009	28.93
2010	29.92
2011	30.76
2012	31.63
2013	32.58
2014	33.53
2015	34.59
2016	35.6