*Excludes Observations that spanned multiple years

Pre 197022
19702
19711
19720
19730
19740
19752
19760
19770
19780
19791
19801
19810
19820
19830
19841
19850
19860
19870
19881
19892
19902
19910
19921
19936
19942
19952
19969
19972
19981
19992
20000
20010
20023
20030
20040
20050
20060
20070
20080
20090
20100
20110
20120
20130
20140
20150
20161
20170
Total64