Portman leads the pack on Forbes magazine's countdown of Hollywood’s Best Actors For The Buck, returning $42.70 (£26.70) for every dollar studio bosses spend on her, thanks mainly to her leading role in indie film Black Swan.
Stewart is second, on the strength of her Twilight films and this year's (12) Snow White and the Huntsman, returning an average of $40.60 (£25.40).
Shia LaBeouf, Robert Pattinson and Daniel Radcliffe round out the top five.
Earlier this month (Dec12), Eddie Murphy topped Forbes' list of the Most Overpaid Actors of 2012. He returned an average of just $2.30 (£1.40) at the box office for every dollar he earned.