How Liquidity by Session Can Change During Volatile Markets

Liquidity by session: the core idea

“Liquidity by session” describes how trading activity and market depth tend to vary across different hours when major centers are open and overlap. In practical terms, liquidity is easier to access when many participants are active and ready to place orders; it becomes harder when fewer participants are trading.

A simple way to picture this is a “queue of available prices.” When more orders sit in the market (more depth), a transaction can usually match at prices closer to where it was expected. When fewer orders are present (less depth), the next available price may be farther away.

Why volatility can change liquidity patterns

Volatile markets change liquidity not just by increasing price movement, but by changing how orders arrive, how quickly they can be matched, and whether participants keep providing quotes.

1) Gaps: fewer matches between the last quote and the next one

During volatility, price can move faster than the market can update. If liquidity thins, there may be fewer resting orders at intermediate prices. That makes it more likely that the “next available level” is reached directly, creating a gap between where a price was when an order was decided and where it can be executed.

Mechanism summary:

• Higher volatility increases the chance that your order “misses” the intended price level.
• Lower depth means there are fewer resting orders to absorb the move.
• The result is wider jumps and less stable spreads around the transition between session conditions.

2) Latency: timing differences between order submission and execution

Latency is the time delay between when an order is submitted and when it is processed and matched. In volatile conditions, prices can change significantly during that delay. Even if liquidity exists, the effective liquidity you experience is the liquidity available at the moment of execution—not the moment you triggered the order.

Material limitation:

• Latency makes execution more dependent on short-lived conditions.
• Two identical orders can experience different results if volatility accelerates during the brief delay.

3) Liquidity withdrawal: participants may reduce depth when uncertainty rises

Some market participants adjust their behavior in response to rapidly changing conditions. When uncertainty increases, they may widen their quoted prices or reduce the amount of size they are willing to place at tighter levels. This is often described as liquidity “pulling back.”

What changes across sessions:

• In quieter periods, more participants may be willing to provide depth.
• In volatile periods, even during normally active hours, the effective depth at certain price levels can shrink.

Failure mode:

• Liquidity can drop when you most need it, precisely because the market conditions make quoting riskier.

4) Order handling: how orders interact with the available book

Even with identical market-wide “liquidity by session,” the realized execution depends on how orders are handled. Important general factors include:

• Whether the order is matched immediately or waits for a better price level.
• How the system chooses which available price levels to fill.
• How partial fills are treated when available depth is insufficient.

Simple example model (assumptions stated):

• Assume at 10:00 a session open, there is enough depth for a desired size at a range of prices.
• During volatility, assume that depth at the near price level drops, leaving only smaller resting size at that price.
• An order larger than that near-level depth will be partially filled there, with the remainder filled at worse available levels.

No outcome is guaranteed in real markets, but this model explains why execution quality can degrade when liquidity thins.

Limitations and risks to keep in mind

1. Liquidity is not a single number. Liquidity can vary by price level, time, and size. “By session” is a directional description, not a constant rule.

2. Relationships may not hold in stress. Historical patterns across sessions can break during sudden volatility, news-driven moves, or when participants withdraw.

3. Execution can differ from expectations. Even if you observe a quoted price, actual fills depend on the available next levels at execution time, which volatility and latency can shift.

4. Different market structures produce different effects. The degree to which gaps, latency sensitivity, and depth withdrawal appear depends on the trading venue and the execution approach.