To represent as being higher or greater than it is.(verb)
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Use "overrepresent" in a sentence
"It's fair to say most of these polls overrepresent democrats so the situation leading up to the 2010 elections is likely worse for democrats than the poll indicates."
"If an area is drawn to overrepresent conservative voters, then that area will always elect conservatives."
"What the Senate does is arbitrarily overrepresent certain places, and most of those places are rural."