*Excludes Observations that spanned multiple years

Pre 19700
19700
19711
19720
19730
19740
19750
19760
19770
19781
19790
19800
19810
19820
19830
19840
19850
19860
19872
19882
19890
19905
19917
19923
199327
19940
19950
19960
19970
19980
19991
20000
20010
20021
20030
20040
20050
20060
20070
20080
20091
20100
20110
20121
20130
20140
20150
20160
201712
20180
20190
20200
Total64