The town, and village, of Coventry are in Chenango Co, the county directly sourth of Madison Co. I don't think, without checking, that it was ever in Broome Co, but could be mistaken. As to why/how someone is "missing" on a census, I have a couple of theories. Might it be possible that, for some reason we will never know, they moved to another place, without selling the land on which they lived in the earlier census, and then moved back to that land after the 1880 census. A long shot. More likely, I think, is the theory that the enumerator simply missed the family, or that he did enumerate them but when the final census sheet was written they were at that time missed. I don't know it to be a fact, but it seems to be logical that the census pages we see today were the final draft, and that a rough draft or maybe just sheets of paper was carried around by the actual enumerator, to avoid loss of, or spoilage of, the final page. Further, it "appears" that possibly, in some cases anyway, that the person who made the final draft was someone in "census headquarters" at the county level, who rewrote the rough drafts brought in by the various enumerators ... and often seems to have had trouble with their handwriting to boot when he made the transcriptions. Just a theory though. Graham Louer