*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
198756
19889
19892
19903
199122
19923
199340
19944
199526
199639
199752
19983
19992
20001
20010
20020
20030
20048
20050
20060
20071
20081
20090
20100
20110
20120
20130
20141
20151
20160
20171
20180
20190
20200
20210
Total275