Year	Number
1971	16.97917
1972	11.26991
1978	10.23551
1992	11.25197
1994	10.30909
1995	10.25448
1996	10.12892
1997	10.27046
1999	10.29643
2001	10.76449
2004	11.11191
2008	5.80925
2015	8.12069
2017	8.54364