Liquidity, and why it is not the same as volume

Three published quantities are used as proxies, and each captures a different part of the picture. The bid-ask spread is the difference between the best price at which someone will buy and the best price at which someone will sell. A narrow spread means the cost of entering and leaving immediately is small, which is a necessary condition for liquidity but not a sufficient one: a market can show a tight spread for a tiny size and widen sharply beyond it.

Order-book depth is the total size resting at prices within a given distance of the mid-price. It answers the question the spread does not: how much can be traded before the price moves by a stated amount. Depth is the closest of the three to the definition of liquidity, and it is also the hardest to observe, because it changes from second to second and because some resting orders are not genuine — they are placed to create an impression and cancelled before they trade.

Reported volume is the third proxy and the weakest. It measures how much traded, not how easily it could have traded. A market can process enormous volume while moving violently, which is the opposite of liquidity. Volume is also the figure most susceptible to manipulation, a problem taken up in detail on the trading volume page. A reader who treats volume as a liquidity measure will systematically overstate how easily large positions can be moved.

In its early years Bitcoin was traded on a handful of venues, most of them small, several of them unreliable, and at least one of them fraudulent. Spreads were wide, depth was thin, and a modest order could move the price by several per cent. The 2011 and 2013 price records reflect that environment: the extremes in those years were reached in markets that could not have absorbed institutional size, and the figures should be read with that in mind.

The market deepened substantially through the 2017 cycle and again through 2020 and 2021. More venues, better infrastructure, regulated futures, and eventually spot exchange-traded funds all added capacity to absorb orders. The practical effect is that the same dollar order moves the price far less today than it would have a decade ago. That is a genuine improvement in market quality, and it is one of the reasons the percentage moves in recent cycles have been smaller than those in the early record.

The improvement is not uniform. Liquidity concentrates in the largest venues and thins sharply during stress. When the market falls quickly, market makers withdraw, spreads widen, and depth evaporates precisely when participants most want to trade. The liquidity observed on a calm day is not the liquidity available on a violent one, and the difference can be an order of magnitude. That asymmetry is a structural feature of market making rather than a flaw in any particular venue, and it is why the drawdown record shows deeper declines in the earlier, thinner years.

The exchange price differences page explains how the gaps between venues relate to liquidity, and the market capitalisation page explains why a capitalisation figure says nothing about how much money could be realised at the quoted price.