Assemblers at toy factories from the North Pole to the South China Sea usually breathe a big sigh of relief this time of the year. That’s because their assembly lines are winding down from the peak season.

However, the $84 billion market for action figures, building sets, dolls, games, play sets, puzzles, radio-control helicopters, slot cars, teddy bears, trains, trucks and other toys remains relatively steady throughout the year—not just in December.