Corporate giant Wal-Mart, which employs nearly 1 out of every 100 people in the American workforce, has announced it will raise its minimum wage in April to $9, a move that will affect an estimated half a million workers.

The move could be a sign that the public's expectations of corporate responsibility are changing, said Harvard historian Nancy Koehn, who pointed out that Wal-Mart had been underpaying employees for years to maximize profits.

"At least part-time Wal-Mart employees have a very, very hard time making ends meet on the salaries and the hours that Wal-Mart offers," Koehn said. "There are many full-time workers who can't feed a family of four above the poverty line."

On the other hand, Koehn pointed out that the move is also a potential PR boost for Wal-Mart, which has attracted sharp criticism for its low wages in the past. 

"As they've tried in many ways to get ahead of their environmental black name, they're trying here to switch the perception of Wal-Mart and what kind of employee they are," she said.

But while Koehn touted the move as smart business, she said the larger issue of rising inequality in the United States should be cause for concern.

"Americans are playing by the rules of the game, playing by all the rules, walking and driving the American highway, and can't get above the poverty line," Koehn said. "The question is: what does that say about the society we live in?" 

To hear more from historian Nancy Koehn, tune in to her full interview on Boston Public Radio above.