Some people look at income inequality and shrug their shoulders. So what if this person gains and that person loses? What matters, they argue, is not how the pie is divided but the size of the pie. That argument is fundamentally wrong. An economy in which most citizens are doing worse year after year—an economy like America’s—is not likely to do well over the long haul.Well, THAT argument is worse than fundamentally wrong. As economists these days are wont to put it, that isn't even wrong. One's person's prosperity doesn't have to come at the expense of another. It can, say, in the form of rent (privilege) seeking that is designed to limit your competitor's ability to challenge your position. For instance, in unionized public employees working to keep their local monopolies free from other options for the nation.
However, the 1% usually aren't that at all (though they do benefit, as we all do, from stable laws that provide security). They are entertainers (LeBron James, Julia Roberts) who we're free to ignore, and entrepreneurs like Bill Gates who made their fortunes by providing literally trillions of dollars of value to their customers.
Not to mention the higher wages the working classes earn by having the 1%'s capital to use in their daily endeavors--the highest wage countries are those like the U.S. and Japan which also have the highest amount of capital per capita.
There are sound economic reasons (even if we ignore the moral ones) for discouraging people from coveting their neighbor's wealth; if earned in the marketplace, it's re-payed the rest of us many times over in the goods and services we enjoy.
For his efforts, Stiglitz should be awarded an Ignoble Award in Economics too. If he were true to his science he would be encouraging the 1% to re-invest their gains in attempts to make even more money. Because, by their so doing they would increase the producer surplus available to, even, the poor.