*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
19870
198825
19890
19900
19911
19922
19932
19940
19950
19962
19976
19983
19990
20001
20011
20021
20034
20040
20053
20067
20073
20082
20091
20100
20110
20120
20130
20140
20150
20160
20170
Total64