What is an undervote?

An undervote occurs when the number of choices selected by a voter in a contest is less than the maximum number allowed for that contest or when no selection is made for a single choice contest.[1] An undervote can be intentional for purposes including protest votes, tactical voting or abstention. Alternately undervotes can be unintentional and caused by many factors including poor ballot design. Undervotes combined with overvotes (known as residual votes) can be an academic indicator in evaluating the accuracy of a voting system when recording voter intent.[2]