Year	Number
1972	25.11017
1974	25.49091
1975	23.78043
1976	21.64122
1977	26.04296
1978	24.53865
1979	24.50513
2000	18.74101
2007	21.50372
2008	17.12889
2009	16.22446
2010	15.0656
2011	14.51203
2012	13.84503
2014	14.2465
2015	14.33428
2017	12.05576
2018	12.40564