Year	Number of
1990	28.6
1991	27.9
1992	26.13
1993	23.81
1994	23.04
1995	22.53
1996	22.32
1997	21.76
1998	24.47
1999	25.51
2000	23.94
2001	24.14
2002	23.65
2003	23.16
2004	23.25
2005	23.42
2006	23.72
2007	23.36
2008	24.28
2009	23.1
2010	23.13
2011	23.57
2012	24.15
2013	25.18
2014	26.59
2015	26.4
2016	26.64