*Excludes Observations that spanned multiple years

Pre 19700
19700
19710
19720
19730
19740
19750
19760
19770
19780
19790
19800
19810
19820
19830
19841
19850
198613
19870
19882
19890
19900
19916
19922
19938
19948
19954
19962
19973
19980
19990
20000
20012
20020
20030
20040
20056
20061
20070
20080
20090
20104
20112
20120
20130
20140
20150
20160
20170
Total64