Year	Number of
1990	10.47
1991	11.42
1992	12.59
1993	13.51
1994	15.57
1995	17.25
1996	18.74
1997	21.43
1998	22.23
1999	22.75
2000	23.05
2001	24.41
2002	24.79
2003	24.76
2004	25.14
2005	25.12
2006	25.86
2007	26.58
2008	27.84
2009	29.11
2010	29.56
2011	30.57
2012	31.9
2013	32.11
2014	31.98
2015	32.87
2016	34.06