What an effect-size matrix is trying to say
Comparing sleep supplements by effect size, rather than by popularity, separates how reliably something works from how often it is sold. In broad terms, melatonin has the clearest evidence for shifting sleep timing and modestly shortening sleep onset, especially for circadian problems. Magnesium tends to help most in people who are deficient. Glycine, L-theanine, valerian, and apigenin (the calming flavone concentrated in chamomile) generally show smaller or less consistent effects in controlled studies.
Use case matters as much as raw effect: a compound useful for jet lag is not necessarily the right tool for stress-driven wakefulness.
Interpreting the rankings responsibly
Effect sizes here are approximate and drawn from heterogeneous trials with varying doses, formulations, and populations, so the ordering should be read as a rough guide rather than a precise league table. Many of these agents are mild, and none is a substitute for evaluating the cause of persistent insomnia.
This is general educational information, not medical advice. Persistent sleep problems should be assessed by a qualified healthcare professional.