Year	Number of
1990	22.39
1991	22.54
1992	22.84
1993	22.64
1994	23.7
1995	24.1
1996	23.55
1997	23.92
1998	24.08
1999	23.8
2000	24.09
2001	24.11
2002	25.42
2003	26.77
2004	28.45
2005	29.61
2006	30.12
2007	30.68
2008	31.87
2009	31.89
2010	32.15
2011	32.44
2012	31.43
2013	31.23
2014	32.43
2015	32.66
2016	32.94