Compulsively checking your 401(k) is seen by behavioral economists as the source of bad investment decisions. Right now, though, looking at your portfolio too seldom could equally lead to missed opportunities.

In its 2024 outlook, asset-management giant BlackRock presented an interesting thought experiment: If you had perfect foresight and could shift your U.S. stock investments once or twice a year toward the best-performing sector, how much would you gain? As it turns out, much more than before.