Year	Number of
1990	34.12
1991	33.58
1992	34.94
1993	34.14
1994	34.95
1995	33.75
1996	32.63
1997	31.63
1998	31.61
1999	31.91
2000	31.02
2001	29.84
2002	29.54
2003	27.84
2004	27.97
2005	27.57
2006	26.49
2007	24.79
2008	26.38
2009	26.65
2010	25.54
2011	27.26
2012	28.15
2013	29.04
2014	29.94
2015	30.81
2016	31.74