One possibility relates to the extreme brevity of the summaries: because the summaries are only 350 words in length, it is possible to have two summaries of the same meeting which are equally good but completely non-overlapping in content.
to further gauge speaker activity, we located areas of high speaker interaction and indicated whether or not a given dialogue act immediately preceded this region of activity, with the motivation being that informative utterances are often provocative in eliciting responses and interaction.