Beyond the Hype: our Research Shows What Really Moves Stock Prices

Main Takeaway

For decades, asset pricing has been dominated by fundamentals. New research proves this view is incomplete.

The primary mechanical driver of stock prices is not fundamentals, but the force of institutional order flows.

For every dollar of net institutional investment into the broad market, the total market capitalization moves by an astonishing $7 to $10.

This powerful multiplier effect, empirically validated for the first time with high-frequency data from Exponential Technology, confirms that the sheer force of large-scale buying and selling is the dominant factor in price determination across most time horizons.

This finding has critical implications for how we should think about alpha generation, trade execution, and market risk.

Study Highlights

Groundbreaking Proof: For the first time, this study uses minute-level institutional order flow data to empirically validate the Inelastic Markets Hypothesis (IMH), establishing order flow as the primary mechanical driver of market prices.

Bridging Key Theories: The research connects the Gabaix-Koijen macro-level theory of inelasticity with Bouchaud's microstructural Latent Liquidity Theory, showing how high-frequency trading dynamics aggregate to create large-scale market movements.

Dominant Explanatory Power: Institutional order flows are proven to explain the vast majority of market movements, accounting for 62% of quarterly and over 75% of daily open-to-close price changes in major U.S. equity indices.

Confirmation of Price Impact Decay: The study documents a systematic decay in the multiplier effect over time, from approximately 10x at a daily frequency to 7.2x at a quarterly frequency, confirming theoretical models of transient vs. permanent price impact.

Passive Investing is Increasing Market Fragility: The study provides the first empirical proof that market inelasticity has increased over the past decade. After controlling for market liquidity conditions, the multiplier effect is shown to be trending higher, a direct consequence of the growth in passive and systematic investing. This means each dollar of institutional flow has a greater market impact today than it did ten years ago.

About Market Inelasticity

The Inelastic Markets Hypothesis (IMH) challenges the long-held Efficient Market Hypothesis (EMH), which posits that stock prices always reflect all available information about a company's fundamental value. In contrast, the IMH argues that the market is largely "inelastic." This means prices must move significantly to accommodate the massive buying and selling flows from large institutional investors (like pension funds and mutual funds) who often trade based on fixed mandates, regardless of price.

This relationship is quantified by the "GK multiplier," named after the researchers Gabaix and Koijen. This multiplier measures how much the total value of the stock market changes for every dollar of net flow. This means that for every $1 of net investment into the broad stock market, the total value of the market increases by approximately $7 to $10. This disproportionate impact occurs because there are no easy substitutes for the market as a whole, forcing prices to absorb the pressure from large capital flows.

Inelasticity Across Markets & Timescales

The study measured this inelastic effect at different levels of the market—from the entire index down to individual stocks—and found a clear, hierarchical pattern. This structure fundamentally changes how we should think about portfolio risk and execution strategy.

1. Aggregate Market (Index-Level) Results

For broad market indices like the S&P 500, the multiplier effect is at its strongest. The study found that the daily multiplier is approximately

while the quarterly multiplier is

The higher daily number reflects a powerful but temporary impact from order book depletion that fades slightly over subsequent weeks as liquidity returns to the market. The explanatory power of these flows is immense, accounting for over 75% of daily price movements in the S&P 500.

2. Sector-Level Results

Market inelasticity varies significantly by industry sector, driven by a concept called "substitutability"—how easily an investor can find a similar alternative investment. Sectors with few close substitutes are more inelastic, meaning flows have a much larger price impact. The table below highlights the dramatic difference between the most and least inelastic sectors.

Sector	Average Multiplier (ℳ)
Energy (Highest)	10.51
Health Care	7.57
Information Technology	5.62
Materials (Lowest)	3.58

The practical implication is striking: a $100 million net flow into the Energy sector corresponds to a market cap increase of over $1 billion. In contrast, the same $100 million flow into the Materials sector results in a much smaller $358 million increase.

3. Individual Stock-Level Results

At the single-stock level, the multiplier collapses to

on average. This is the final piece of the puzzle, confirming that market inelasticity is a macro phenomenon. While it is difficult to find a substitute for the entire S&P 500, it is very easy for an investor to substitute one technology stock for another. Because of this high substitutability, the price impact of flows is much lower, and its predictive power is weaker, explaining only about 16% of a single stock's price movement.

Summary

The evidence presented in this research is clear and compelling: institutional order flows are the dominant mechanical force driving market prices.

This research provides a new lens for viewing the market, with profound implications for execution, risk, and alpha generation.

These insights, once hidden, are now quantifiable through the XTech US Equity Flow dataset—the key to decoding modern market mechanics.

About XTech Flow™ US Equity Flow Analytics

Powered by Exponential Technology and based on LSEG data, XTech Flow™ US Equity Flow Analytics utilizes the US Consolidated Feed to apply deep high-frequency trading knowledge.

This identifies the direction of active risk-taking by institutional buy-side, market makers, and retail traders. With unprecedented 1-minute granularity and 15 years of history, the dataset provides a unique ability to distinguish institutional and retail flow, offering near-real-time market intelligence across the entire US equity market.

Search our full dataset library from our Data Catalog