I inadvertently found out that a colleague who shares my duties earns a lot more than I do. While he has a bit more seniority, it's not enough to justify this gap. I want to ask for a raise but don't know what to say. Meanwhile, I find I'm resenting my co-worker, even though this isn't his fault.—Anonymous, New York
Yes, your ire is misplaced, as you've already figured out. And your understandable envy may be about more than just the money.
Unequal pay for the same work can appear unjust. But absent a pattern that's illegal (race or sex discrimination, for instance), such a differential can be reasonable—indeed, inevitable—as employees strike their individual bargains. Beyond tenure, there's the question of who's performing better (worth looking at, hard as that may be). Or a boss may award a hefty raise to keep someone from defecting to a competitor. Then, too, some people are able to be more assertive than others in salary negotiations. It might be useful to look at your own conflicts about asking for more—at work and elsewhere. His ability to do so might be part of what you resent (and envy) about your colleague.
How to approach the boss if you do ask for a raise? In the usual way: Talk about your accomplishments (stressing any skills you have newly mastered), your commitment, your plans for future projects. Resist the temptation to bring up your colleague's salary.
In fact, focusing on yourself—grappling with hard questions and perhaps taking action—is the cure for your smoldering resentment. It beats grumbling aloud when your co-worker leaves early (or for a fabulous vacation) or otherwise turning your preoccupation with his pay into torment or martyrdom. Think of it this way: Your colleague demonstrated that your work could be better compensated. The rest is up to you.