For years, people have claimed that US stocks are more liquid than European ones because of mega-cap behemoths—those $100 billion giants with endless trading activity. But that’s a lazy explanation. Even if you take the giants out of the picture, the US still runs circles around Europe in mid and small-cap liquidity. Let’s break it down.

Liquidity: It’s More Than Just Big Names

If mega-caps were the whole story, then mid and small-caps would trade at similar levels on both sides of the Atlantic. Spoiler: they don’t. The liquidity gap extends across company sizes, showing that deeper factors are at play.

The Numbers Tell the Story

Here’s the hard data:

1. Trading Volume: US mid-cap stocks trade 2-3 times more than their European counterparts. Small caps? 4-5 times more. A deeper pool of buyers and sellers makes all the difference.

2. Bid-Ask Spreads: US stocks have 30-50% tighter spreads, making them smoother and cheaper to trade. When transaction costs are lower, investors are more active.

3. Institutional Interest: US mid and small caps attract way more big-money investors, keeping liquidity flowing. European stocks? Not so much. Without large institutional support, markets become sluggish.

4. Turnover Ratios: US small and mid-caps change hands more frequently, reflecting a market where price discovery happens faster and capital moves more efficiently.

Why the US Leaves Europe in the Dust

It’s not just about company size. The US market has fundamental advantages:

• Retail Traders Make Waves: Commission-free trading, retirement accounts, and an investment culture keep retail money moving. Europe is still playing catch-up. Retail investors in the US actively trade, adding a crucial liquidity layer.

• One Market, One System: The US has a unified market structure. Europe is fragmented, with different exchanges and rules adding friction. Every added layer of complexity slows down trades and makes investing less attractive.

• Market Makers Keep Things Fast: The US has a powerhouse network of market makers and high-frequency traders ensuring constant liquidity. Europe? Not nearly as much. Automated trading in the US ensures that there’s always someone on the other side of a trade.

• More Research, More Coverage: US mid and small caps receive significantly more analyst coverage, increasing investor confidence and participation. In Europe, many small caps go under the radar, leading to lower trading volumes and more illiquidity.

Bottom Line: The Liquidity Gap is Real

Blaming liquidity differences on mega-caps is missing the point. Even in mid and small caps, US stocks are simply easier and cheaper to trade. The solution isn’t just to grow bigger companies—it’s about overhauling market structures, getting more investors in the game, and making trading seamless.
Liquidity isn’t an accident. It’s built through active participants, efficient structures, and a culture of investing. The US has mastered this formula. If Europe wants to compete, it needs to rethink how its markets function and create the conditions for true liquidity to thrive.