*Excludes Observations that spanned multiple years

Pre 19700
19700
19710
19720
19730
19740
19750
19760
19770
19780
19790
19801
19810
19820
19830
19841
19850
19860
19874
19887
19899
19900
19912
19922
19933
19947
19955
19962
19970
19980
19990
20000
20010
20020
20031
20040
20050
20064
20071
20088
20090
20102
20115
20120
20130
20140
20150
20160
20170
Total64