The Quantitative Psychology of Round Numbers in Financial Price Action

What Numbers Say When Traders Start Listening

In the fast-evolving domain of quantitative finance, where trading algorithms scan thousands of variables per second and execution is measured in microseconds, one would expect irrational human behavior to be largely filtered out. Yet even in this hyper-optimized environment, price levels such as $100, $500, or $1,000 continue to wield outsized influence. They are not just numbers — they are psychological milestones. And time and again, they show up where markets hesitate, reverse, or accelerate.