Year	Number
1978	27.97392
1979	27.38779
1983	20.33311
1984	23.46773
1985	21.22519
1989	18.38658
1990	17.80025
1992	17.16806
1999	17.77204
2000	17.56999
2001	17.03586
2002	15.90347
2003	15.80411
2004	15.76766
2005	15.14568
2007	14.54218
2008	13.45642
2009	14.1425
2010	13.00746
2011	13.08663
2014	12.71532
2015	13.40321
2016	13.349
2017	14.09682
2018	13.9917