Year	Number
1983	13.4467
1984	10.10671
1999	31.07948
2005	28.11474
2006	21.87633
2008	23.74567
2009	20.64367
2010	21.40321
2011	20.53927
2012	19.88922
2013	13.7798
2014	14.29917
2015	12.14578
2016	11.41873
2017	11.0089
2018	10.81456