It’s December, which means it’s crunch time for the ultra-wealthy and their menagerie of tax planners, estate lawyers and philanthropic consiglieres to settle their affaires d’etat. The end of the year typically ushers in major offloading of stock by insiders looking to lock in a capital gain (or, if it’s efficient, to harvest a loss). This year has already seen a record $69 billion of stock sales by C.E.O.s, founders and big stakeholders—$20 billion is attributable to Jeff Bezos and Elon Musk alone—as billionaires confront the the specter of higher taxes next year, especially in Bezos’ home state of Washington, which just raised its capital-gains rate.