My family and I traveled to Cambodia. On the day we left to return home, the immigration officer asked me for a tip, and I gave him $5. Was it wrong to pay and, by extension, help perpetuate corruption?  —Leon Weaver, Redding, CT

THERE ARE NO ETHICAL parameters for tipping. It’s hard to fathom why almost everyone tips the pizza delivery person while almost no one tips the UPS driver. Tipping an immigration officer seems odd only because he’s a government employee. But it’s possible he requests tips because he needs the extra money to make a living wage. Of course, it’s equally possible that he’s just a con artist who realizes that most Westerners are relatively affluent and will throw away $5 to avoid even one awkward moment. Here’s my advice: If you suspect the man is making his request out of necessity, give him the money. If you suspect he is trying to con you because you represent an easy mark, give him nothing. If you suspect neither of those things, tip him whatever you think his service was legitimately worth, relative to all the other services you normally reward with tips.
—Adapted from “The Ethicist” in The New York Times Magazine