Year	Number of
1990	23.08
1991	24.83
1992	25.69
1993	26.1
1994	26.18
1995	27.15
1996	27.01
1997	28.27
1998	27.98
1999	28.48
2000	27.95
2001	28.95
2002	28.94
2003	29.2
2004	27.77
2005	29.04
2006	29.7
2007	31.76
2008	33.1
2009	33.74
2010	36.04
2011	36.23
2012	37.04
2013	37.9
2014	38.83
2015	39.81
2016	40.88