Tržní mikrostruktura
Market Microstructure · Short Interest · Float · Volume · Short Squeeze
The mechanics of how the market works — who is buying and selling, how large the volume is, and what happens under technical pressure.
What it is
Market microstructure describes how the stock market technically works beyond fundamentals.
Stock float (freely tradable shares): The number of shares available for trading in the open market — excluding insider shares and shares in lockup. A small float = large price moves even on small volume.
Volume (trading volume): The number of shares traded in a given period. High volume during a price move = more convincing move. Low volume = move less reliable (more manipulable).
Short Interest: The number of shares that investors have borrowed and sold short as a percentage of the float. High short interest (above 15–20% of float) signals that the market is negatively disposed toward the stock.
Short Squeeze: When a stock with high short interest starts rising rapidly → shorts must buy back (cover) → their buying pushes the price higher further → a cascading rise. GameStop 2021 is an extreme example.
Borrow (stock loan): To sell short, a shorter must first borrow the stock from their broker. If the stock is hard to borrow, the cost of shorting is high → shorts are forced to close their positions.
Why track it
Microstructural data is important for:
- →Entry timing: A stock with extremely high short interest may be a candidate for a short squeeze — the price can technically overshoot intrinsic value.
- →Liquidity: Low float + low volume = poor liquidity, wide bid-ask spread, difficult to exit the position.
- →Sentiment: Declining short interest = shorts are capitulating → bullish.
Real-world example
GameStop (GME) January 2021:
- →Short Interest: ~140% of float (more shares borrowed than exist in the float — through chain loans)
- →Reddit community r/WallStreetBets bought in a coordinated fashion
- →Short Squeeze: GME from $17 to $483 in 2 weeks
- →Shorts lost over $20 billion
GME's fundamental value did not change — this was a purely microstructural phenomenon.
Watch out for
Microstructural signals are short-term and unpredictable. Never buy a stock just because it has high short interest — high short interest may be justified (the company has real problems). Fundamentals are primary.