Year	Number of
1990	14.55
1991	14.66
1992	14.72
1993	14.75
1994	14.79
1995	14.91
1996	16.01
1997	17.29
1998	18.81
1999	20.63
2000	22.74
2001	24.35
2002	26.05
2003	27.75
2004	29.6
2005	31.74
2006	31.54
2007	31.45
2008	31.48
2009	31.6
2010	31.8
2011	31.61
2012	31.57
2013	31.56
2014	31.54
2015	31.54
2016	31.55