Duplicate Most Used Terms

I am using the Most Used Terms block on my home page as delivered by OP2.1 out-of-the-box. For some reason, one of the terms that appears in the block -- "Economics" -- appears twice. No other term appears more than once. As I understand it, these terms come from Calais, so is this a Calais problem or something in the definition of the View that provides that block?

Thanks.