Year	Number
1991	25.96184
1998	29.51528
1999	29.24613
2000	28.05968
2001	27.42901
2002	29.68991
2003	29.83536
2004	30.75141
2005	32.90201
2006	30.21484
2007	29.18924
2008	27.71268
2009	25.0476
2015	27.78203
2016	26.84814
2017	27.61705