*Excludes Observations that spanned multiple years

Pre 19700
19700
19710
19720
19730
19740
19750
19760
19770
19780
19790
19800
19810
19820
19830
19840
19850
19860
19871
19880
19892
19901
19910
19920
19930
19940
19950
19960
19973
19982
19990
20000
20010
20023
20030
20043
20050
20062
20071
20080
20090
20100
20111
20120
20130
20140
20150
20162
20170
Total21