*Excludes Observations that spanned multiple years

Pre 19700
19700
19710
19720
19730
19740
19750
19760
19770
19780
19790
19800
19813
19820
19830
19840
19850
19860
19870
19881
19891
19900
19916
19920
19931
19940
19950
19961
19971
19980
19990
20001
20010
20021
20030
20042
20050
20062
20071
20080
20090
20100
20110
20120
20130
20140
20150
20160
20170
Total21