Year	Number
1998	26.20998
1999	24.27073
2000	22.65003
2001	22.52108
2002	20.00645
2003	18.15834
2004	22.72075
2005	20.08085
2006	16.41787
2007	14.51632
2008	13.2588
2009	12.67736
2010	11.70072
2011	12.27511
2012	11.4094
2013	11.19408
2014	12.02005
2015	10.34037
2016	10.29657
2017	10.16278