Year	Number of
1990	13.58
1991	14.08
1992	14.64
1993	15.3
1994	15.98
1995	16.73
1996	17.17
1997	17.74
1998	18.44
1999	19.27
2000	20.29
2001	21.09
2002	22.05
2003	23.2
2004	24.36
2005	25.48
2006	26.08
2007	26.59
2008	27.23
2009	27.89
2010	28.61
2011	28.06
2012	27.39
2013	26.98
2014	26.56
2015	26.39
2016	26.37