What is DIX?
DIX (Dark Pool Short Index) is a metric developed by SqueezeMetrics that measures the proportion of short volume in dark pools for S&P 500 component stocks. Published daily, DIX gained attention for a counterintuitive reading: its creator argues that high dark pool short volume reflects buying, not bets against the market. The dark pool index (DIX) today is the DIX series we publish, one dated reading per session.
In outline, each stock's dark pool short volume is divided by its total dark pool volume, and DIX combines those ratios across the S&P 500 components, weighted by dollar value. SqueezeMetrics' 2018 paper Short Is Long describes it as chronicling, "in dollar-weighted terms, dark pool short volume across all components of the S&P 500". Over the year to 14 October 2026 the series ranged from 39.3% to 52.4%.
Why High Short Volume is Bullish
This is the part that confuses most traders. How can more shorting be a bullish signal? The answer lies in understanding who is doing the shorting and why.
In dark pools, the dominant participants are market makers and large institutional desks. When an institution wants to buy a large block of shares, the market maker on the other side of the trade technically "sells short" to provide that liquidity. The market maker does not hold the shares in inventory, they sell short and then acquire the shares afterward to cover. This is a fundamental part of how market making works.
On that argument, high dark pool short volume reflects market makers selling short to fill customer purchases, so a high DIX is read as buying demand rather than bets against the market, and a low DIX as less of it. It is an inference about who was on the other side: the reported short volume itself describes where volume was printed, not who was buying, and DIX is a derived daily index with no individual trade, size or price in it.
Historical Accuracy
The published evidence comes from SqueezeMetrics itself. In Short Is Long it reports that "Very high relative percentages (≥45%) of dollar-weighted short volume are associated with mean 60-market-day returns of 5.3%, as compared to a mean of 2.8% across the whole dataset." That is the creator's own average over its own sample, not an independent test, and an average 60-day return is not a hit rate for any single reading.
Anecdotes of DIX rising before particular market lows circulate widely; a list of episodes chosen after the fact is not a track record. SquawkFlow does not score DIX and publishes no accuracy figure for it.
How to Read DIX
A high reading: A larger share of dark pool volume was reported as short sales. Under SqueezeMetrics' interpretation that reflects more customer buying filled by market makers; the 45% mark is the one its paper uses.
A low reading: A smaller share was reported as short. Under the same interpretation, less of that buying.
Against its own history: A single reading means more against the series' own range than against a fixed threshold. Our DIX page states where the latest reading sits in its trailing year and dates the shifts in its average level with a change-point method, without reading those shifts as a forecast.
DIX and GEX Together
SqueezeMetrics publishes both DIX and GEX (gamma exposure), and the two answer different questions:
DIX: What share of dark pool volume in S&P 500 stocks was reported as short sales, read by its creator as a proxy for buying.
GEX: A model of how dealer hedging leans, damping moves when positive and amplifying them when negative, built on an assumed dealer side.
Reading them together tells you two things about the same day. It does not produce a forecast, and the four combinations of high and low readings do not come with published hit rates.
Accessing DIX on SquawkFlow
SquawkFlow publishes DIX as a daily series alongside its gamma exposure pages. The public DIX page carries the latest dated reading and a year of daily history with no account needed. Nothing on it is modeled: it shows the published series only.