*Excludes Observations that spanned multiple years

Pre 19700
19700
19710
19720
19730
19740
19750
19760
19770
19780
19791
19801
19811
19820
19830
19840
19850
19860
19870
19880
19890
19900
19910
19920
19930
19946
19952
199656
19976
199828
1999380
20001
20010
200217
20030
200449
20058
200644
200741
200812
200920
201027
20110
20120
20130
20140
20150
20160
20170
Total700