NEW YORK (CNN/Money) - Should U.S. businesses fear the "Attack of the Clones," the upcoming Star Wars sequel? Yes, according to one well-known outplacement firm.

Many of those going to see the highly anticipated film will be workers either calling in sick or otherwise playing hooky from their jobs, according to Challenger Gray & Christmas. It could end up costing the U.S. economy more than $319 million, the firm estimated.

"The positive impact of the movie opening, increased consumer spending on movie tickets and refreshments, as well as increased foreign and domestic tourism and business in shops and restaurants near the movie theaters, could be offset by a spike in absenteeism and subsequent decrease in output," John A. Challenger, the CEO of the outplacement firm, said in a statement last week.

"Star Wars Episode I: The Phantom Menace" drew an opening day audience of 5.7 million people. The Chicago-based company said "Attack of the Clones," which opens in theaters nationwide on May 16, is expected to draw just as many, if not more.

Challenger Gray and Christmas, using government demographic data, believes about half of the audience will be full-time wage or salaried workers. With each earning an average of $122.80 a day, lost wages would total more than $319 million.

The top cities for "Phantom Menace" box office returns were New York, Los Angeles, San Francisco, Chicago and Philadelphia.