*Excludes Observations that spanned multiple years

Pre 19700
19700
19710
19720
19730
19740
19750
19760
19770
19780
19790
19803
19810
19820
19830
19840
19850
19860
19871
19888
19894
19901
19912
19928
19937
19945
19958
19965
199710
19982
19991
20009
200115
20021
20030
20048
20057
20062
20070
200812
20090
201022
201129
20121
20130
20140
20150
20160
20170
Total171