*Excludes Observations that spanned multiple years

Pre 19700
19700
19710
19720
19730
19740
19750
19760
19770
19780
19790
19800
19811
19821
19830
19840
19851
19860
19871
198810
19890
19902
19910
19922
19930
19943
19950
19960
19970
19981
19993
20000
20010
20020
20035
20040
20051
20060
20070
20080
20090
20100
20110
20120
20130
20140
20150
20160
20170
Total31