Year	Number
1996	8
1998	7.96019887924194
2000	9.45273590087891
2002	11.4427862167358
2003	9.95024871826172
2004	8.17307662963867
2005	8.17307662963867
2006	7.692307472229
2007	8.65384578704834
2008	8.65384578704834
2009	8.05687236785889
2010	7.10900497436523
2011	7.0422534942627
2012	6.1032862663269
2013	5.16431903839111
2014	6.40394067764282
2015	5.41871929168701
2016	5.9113302230835
2017	5.9113302230835
2018	5.82524251937866
2019	7.72946882247925
2020	14.9758453369141
2021	14.4927539825439
2022	13.043478012085