Year	Number of
1990	12.34
1991	12.61
1992	13.11
1993	13.38
1994	14.08
1995	15.06
1996	16.2
1997	16.86
1998	17.86
1999	19.13
2000	20.44
2001	20.96
2002	21.69
2003	23.42
2004	24.76
2005	25.75
2006	26.62
2007	26.37
2008	27.12
2009	28.34
2010	28.88
2011	29.5
2012	29.78
2013	30.79
2014	31.85
2015	32.9
2016	33.96