A momentum oscillator that folds real trading volume into the RSI formula — a genuinely useful blend, but still stuck with the same persistence trap.
Gene Quong and Avrum Soudack introduced MFI in 1989, building RSI's momentum logic but weighting it by volume.
Traders adopted 80/20 overbought/oversold bands, inheriting the identical persistence problem RSI has.
MFI became linked to tracking "smart money" flow — evocative language for a fairly mechanical formula.
Serious use reads it alongside trend, valuing its volume-aware divergence most.
MFI multiplies typical price by volume to get "money flow," then applies RSI's same up/down ratio logic to that flow instead of raw price.
In a genuinely strong trend, heavy buying volume keeps MFI pinned high — volume weighting doesn't fix the persistence problem.
When MFI diverges from price with genuinely fading volume behind it, that's a meaningfully stronger warning than RSI's divergence alone — the volume dimension adds real information.
Through that stretch, MFI stayed pinned above 80 with genuinely heavy volume behind every push — real conviction, not a warning.
Near that top, MFI diverged against price while volume itself was visibly thinning — a stronger combined warning than RSI alone offered.
Price is in a strong, sustained uptrend on heavy, genuine volume. MFI reads 90. A trader shorts immediately. Sound?
Price makes a new high while MFI makes a lower high AND the volume behind that new high is visibly thinner than before. How should a trader weigh this?
A trader assumes MFI and RSI will always show identical readings on the same instrument, since both are momentum oscillators. Accurate?
Price above, MFI below, watched tick by tick on the left — and the mark it leaves in the ledger on the right. A confirmed volume-backed divergence, its mirror image — and a false overbought that just kept climbing on real volume.
Price makes a new high. Judge whether MFI genuinely disagrees — then call it: a real divergence, or just confirming momentum.
The classic error is assuming volume-weighting makes the 80/20 crossing safer to trade alone. The discipline is mechanical: check the prevailing trend first, then weigh a genuine divergence more heavily when fading volume backs it up.
Blending volume into RSI's formula produces a genuinely stronger divergence tool — but no formula erases the need to read the trend before the level.
Volume precedes price.