Year	Number of
1990	11.71
1991	12.06
1992	12.45
1993	12.89
1994	13.37
1995	13.89
1996	14.43
1997	15.04
1998	15.7
1999	16.41
2000	17.18
2001	17.96
2002	18.76
2003	19.61
2004	20.49
2005	21.42
2006	22.16
2007	22.91
2008	23.7
2009	24.5
2010	25.35
2011	26.01
2012	26.74
2013	27.5
2014	28.3
2015	29.16
2016	30.09