Year	Number
1998	24.31389
1999	24.81574
2000	24.54567
2001	25.2846
2002	25.84048
2003	25.81875
2004	26.72391
2005	26.78367
2006	26.96494
2007	26.96945
2008	27.2664
2009	23.92415
2010	26.71136
2011	26.80157
2012	26.6305
2013	25.30301
2014	24.91574
2015	24.58869
2016	24.1792
2017	23.78705