Bill Williams Market Facilitation Index

What is the Bill Williams Market Facilitation Index?

The Bill Williams Market Facilitation Index (BW MFI) measures how much price movement each unit of volume produced: the bar's high minus its low, divided by its volume. Williams introduced it in Trading Chaos as a gauge of how efficiently the market is facilitating trade. Rising values mean each unit of volume is moving price further; falling values mean volume is buying less range. It shares an acronym with, but is otherwise unrelated to, the Money Flow Index.

The index is read jointly with volume, giving four bar states: MFI up with volume up ('green', a participated move), both down ('fade', a dying market), MFI up with volume down ('fake', movement without backing), and MFI down with volume up ('squat', heavy volume producing little range). The squat draws the most attention: it is effort without result, a battle at one price that Williams argued often appears near turns and breakout points, without itself saying which way things resolve.

How traders use it

• Classifying bars during a move: strings of green bars support continuation, while a squat after an extended leg warns that the move is meeting genuine opposition.
• Fading unsupported pushes: a fake bar, range expanding while volume shrinks, suggests the move lacks participation and is vulnerable to retracing.
• As context inside Williams' framework: he read BW MFI alongside his Alligator and fractals rather than as a standalone trigger, and most modern uses keep it as a filter, not a signal.