Year	Number of
1990	12.41
1991	12.72
1992	13.52
1993	14.32
1994	14.86
1995	15.17
1996	15.65
1997	16.36
1998	17.25
1999	18.63
2000	19.52
2001	20.61
2002	21.75
2003	22.5
2004	23.39
2005	24.14
2006	25.05
2007	25.98
2008	27
2009	27.93
2010	29.06
2011	30
2012	31.15
2013	32.96
2014	34.24
2015	35.04
2016	35.79