Instructions: Given a text, write a compressed version of it in a single sentence.
Input: The sixth row, labeled "Unknown" shows some First-Class Mail that cannot be identified with any of the aforementioned four sectors. This mail is insignificant, except for FY 1987, the first year the study was conducted.
Output:
The sixth row, labeled "Unknown" shows some First-Class Mail that cannot be identified with any of the four sectors. This mail is insignificant.