SEATTLE — Already tired of the holiday season? Stressed out about what to buy? Whatever you choose, your kids will probably hate it anyway. What a waste. If it’s any consolation, economists largely agree with you. A gloomy bunch, them. But perhaps, even if you blow the gift, the giving act itself can eclipse the blunder. Gift giving, the loose consensus goes, is economically inefficient. You’re spending time, effort, money to try to guess what your loved one wants. At best, you’ll guess right and buy what your loved one would have bought themself. At worst, you’ll buy a sweater that will sit i…