Year	Number
1972	20.67143
1973	11.58779
1974	11.19014
1975	10.99315
1976	12.34091
1977	13.56489
1978	12.72662
1979	13.25735
1980	12.85816
1982	12.88112
1983	12.63448
1984	12.58621
1985	12.54167
1999	11.22951
2000	11.8629
2001	11.74242
2008	5.45277
2009	5.87589
2016	16.8
2017	15.04762