The Swimming Pool

Imagine two swimming pools.

The first is an Olympic-sized pool, filled with millions of litres of water.

The second is a small inflatable pool in a backyard.

Now imagine dropping a basketball into each one.

In the Olympic pool, the water barely notices.

The surface ripples for a moment and quickly settles.

In the inflatable pool, the water splashes everywhere.

The same basketball.

Completely different impact.

Why?

Because the amount of water was different.

Financial markets behave in much the same way.

Think of every buy and sell order as dropping something into a pool.

In a highly liquid market, thousands of buyers and sellers are waiting to trade at almost every price.

A single order barely makes a difference.

The market absorbs it with ease.

But in a market with very few participants, even a relatively small order can cause prices to move dramatically.

The market simply doesn't have enough liquidity to absorb the trade.

This is why some of the world's largest companies often move only a fraction of a percent despite billions of dollars changing hands every day.

At the same time, a small company with very few buyers and sellers can rise or fall several percent because of a single large order.

The difference isn't always the company.

It's the liquidity.

Liquidity is the market's ability to absorb buying and selling without causing large changes in price.

The deeper the pool, the bigger the splash it can absorb.

The shallower the pool, the more every splash matters.

Now think about something else.

Imagine you're standing beside both pools holding a bucket of water.

If you pour that bucket into the Olympic pool, almost nobody will notice.

But pour the same bucket into the small inflatable pool...

...and the water level changes instantly.

The same idea applies to markets.

In a highly liquid market, moving the price significantly requires enormous buying or selling.

In a thin, illiquid market, it may take surprisingly little.

This is one reason professional traders are cautious when trading illiquid assets.

Not only do prices move more violently...

...they are also much easier to influence.

Imagine a small farmers' market where only a handful of people are buying and selling apples.

If one buyer suddenly decides to purchase almost every apple available, prices could double within minutes.

Now imagine trying to do the same thing in a supermarket chain that stocks millions of apples across hundreds of stores.

One customer simply cannot influence the overall price.

Financial markets behave in exactly the same way.

A market with very few participants can sometimes be pushed higher or lower by a relatively small number of trades.

A deep, liquid market requires enormous amounts of buying or selling before prices move significantly.

This is why experienced traders often prefer markets with high liquidity.

The prices are generally more stable.

Bid-ask spreads tend to be smaller.

Large orders are executed more efficiently.

And it becomes much harder for any single participant to distort prices.

The next time you see a sudden price jump, don't immediately ask,

"What happened to the company?"

Instead, ask,

"How deep was the pool?"

Sometimes, the biggest moves happen not because someone placed an enormous order...

...but because there simply weren't enough buyers or sellers to absorb an ordinary one.

Understanding liquidity is about understanding the strength of a market.

The deeper the market, the harder it is to move.

The shallower the market, the easier it is to disturb.

And that's why liquidity is one of the invisible forces behind every price movement you'll ever see.