Observed change log for this dataset, built by diffing consecutive daily builds. A change may come from the state agency amending or withdrawing a notice, OR from an improvement to this project's parser/normalizer. We do not guess which; cause_class labels only what is mechanically distinguishable. change_type=row_absent means the row stopped appearing in our build, not necessarily that the employer withdrew the notice.

Columns: observed_date, prev_observed_date, id, state, company, notice_date, change_type, cause_class, field, old_value, new_value