Year	Number of
1990	29.87
1991	29.65
1992	29.09
1993	28.76
1994	29.27
1995	29.65
1996	29.43
1997	30.11
1998	31.2
1999	31.32
2000	31.7
2001	32.23
2002	32.11
2003	31.28
2004	30.85
2005	30.91
2006	31.77
2007	33.06
2008	34
2009	34.49
2010	34.81
2011	34.87
2012	35.26
2013	35.64
2014	36.41
2015	37.77
2016	39.41