Year	Number of
1990	12.27
1991	12.72
1992	13.25
1993	13.88
1994	14.62
1995	15.46
1996	15.99
1997	16.61
1998	17.23
1999	17.87
2000	18.53
2001	19.08
2002	19.54
2003	19.93
2004	20.28
2005	20.68
2006	21.51
2007	22.44
2008	23.39
2009	24.38
2010	25.4
2011	26.51
2012	27.66
2013	28.89
2014	30.15
2015	31.45
2016	32.77