Beyond the Hype: this Research Shows What Really Moves Stock Prices
For decades, asset pricing has been dominated by fundamentals. This 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 Efficient Market Hypothesis (EMH), which assumes prices always reflect fundamental value. Instead, IMH argues that prices must move significantly to accommodate massive flows from institutional investors trading on fixed mandates, regardless of price.
The "GK multiplier" (named after researchers Gabaix and Koijen) quantifies this effect: for every $1 of net investment into the broad market, total market value 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 large capital flow pressure.
Inelasticity Across Markets & Timescales
The study revealed a clear hierarchical pattern of inelastic effects across market levels, fundamentally changing how we approach portfolio risk and execution strategy.
1. Aggregate Market (Index-Level)
For broad indices like the S&P 500, the daily multiplier is M=10, falling to M=7.2 quarterly as liquidity returns.
These flows explain over 75% of daily S&P 500 price movements.
2. Sector-Level
Inelasticity varies by sector based on "substitutability"—how easily investors find alternatives.
Sectors with fewer substitutes show larger price impacts.
A $100M flow into Energy increases market cap by $1B+, while the same flow into Materials yields only $358M.
3. Individual Stock-Level
At the single-stock level, the multiplier drops to M≈5, explaining only 16% of price movements.
This confirms inelasticity is a macro phenomenon—while substituting the entire S&P 500 is difficult, substituting individual stocks is easy, reducing flow impact.