Year	Number
1979	5.41176
1982	5.0274
1983	5.78873
1984	4.46667
1985	4.55263
1988	6.27419
1996	17.57962
2004	13.20809
2005	12.62644
2006	7.90291
2007	4.87458
2008	13.92973
2009	12.76712
2010	9.26291
2011	10.92083
2012	6.95455
2013	9.83898
2014	9.96479
2015	10.17518
2016	10.14377
2017	10.58306
2018	7.71379