Market liquidity and why it changes your costs

Liquidity is the concept that decides your costs and the quality of your fills, and it is rarely
explained concretely. It is not abstract — you see it every day, as the spread.

1. A practical definition

Liquidity is the ability to buy or sell a quantity without moving the price
appreciably. A liquid market has many resting orders at every price; an illiquid one has a
thin book.

2. Where you see it

• Spread — the most direct indicator. A deep book keeps
  Bid and Ask close together.
• Slippage — a large order in a
  thin market eats through several price levels.
• Gaps on the chart — price jumping across an area where there were no orders.

3. Liquidity changes by the hour

In UTC:

• 21:00–06:00 — the Asian session. Moderate liquidity, good for JPY and AUD
  pairs.
• 08:00–17:00 — the London session. The
  highest liquidity and the tightest spreads on European pairs.
• 12:30–16:00 — the London/New York overlap. The peak of the day.
• 20:00–22:00 — the changeover. The thinnest stretch and the widest spreads; avoid
  opening new positions.

4. When liquidity disappears

• The seconds around a major data release — market makers pull their quotes to
  avoid risk. Spreads widen several times over.
• Public holidays in a major financial centre — if London or New York is closed, the
  whole day is thin.
• The turn of the calendar year — from mid-December into early January, volume drops
  noticeably.
• Late Friday afternoon — desks close positions ahead of the weekend.

5. Why this matters to your costs

Same strategy, same instrument: cost can differ by 50–100% purely from when you press the button. If
you budget with the advertised spread but trade in thin hours, every expectancy figure you have is
wrong.

6. Three things to do

• Measure the average spread in the exact hours you trade, over a week, and use that
  number for all your calculations.
• Avoid opening new positions during the changeover and immediately before major
  news.
• Use limit orders when liquidity is uncertain — they protect you from the spread
  blowout that a market order cannot
  avoid.

This article is for information only and is not investment advice. Conditions and fee levels are published by the brokers and can change at any time — check with the broker you actually use. Leveraged forex and CFD trading carries a high level of risk and can cost you your entire deposit.