What defines a "vast majority"

Hugh Hewitt said of the 700-mile fence at the U.S.-Mexico border:

"...the vast majority of people believe the 700 miles of fencing will in fact be effective..."

A Quinnipac University poll taken in mid-November asked:

As you may know Congress has passed and President Bush has signed legislation that would build a 700 mile fence and increase security along the Mexican-U.S. border. Do you think additional measures are needed from Congress to deal with illegal immigrants entering the country or do you think this is enough for now?"

Only 24 percent said that the fence was "Enough for Now". If it's so effective, how come it's not enough?