Year	Number
1972	30.84255
1974	21.17791
1975	26.57025
1976	21.8115
1977	19.34916
1978	15.42162
2000	13.39086
2009	12.62094
2010	12.15562
2011	11.96742
2012	11.59474
2014	11.98368
2015	11.48074
2017	9.64207
2018	9.29704