The thing that took me a long time to accept is that the Fed does not control most of the dollars in the world. It controls the ones inside its own plumbing, the reserves and the domestic banking system, and those are real. But there is a much larger pool of dollars that exists on the balance sheets of banks outside the United States, created by lending between institutions that never touch the Fed directly, and that pool is where a lot of the pressure that hits your positions actually comes from. If you have ever watched emerging market currencies and crypto both fall apart in the same window and wondered what the common cause was, you were probably looking at this without a name for it.
The name is the eurodollar system, which has nothing to do with the euro. A eurodollar is just a dollar deposit sitting in a bank outside US jurisdiction. The prefix stuck from the early days when a lot of these deposits were held in European banks, and it never got updated even though the same thing now happens in London, Tokyo, Singapore, and the Caribbean booking centers. A Korean bank lends dollars to a Brazilian company. A Japanese fund borrows dollars to buy Treasuries and hedges the currency. None of that is a US bank making a domestic loan, and yet every leg of it is denominated in dollars and creates a dollar obligation somewhere.
Why the domestic numbers miss most of it
When people quote the money supply, they usually mean a domestic aggregate. That is a measurement of dollars inside the US banking system. It is a real number and it is not the whole picture, because dollar credit created offshore does not reliably show up in it. A bank in Singapore can extend a dollar loan and that credit is genuinely part of global dollar liquidity, but it lives outside the domestic count. So you end up with a situation where the officially measured dollar supply looks calm and the actual availability of dollars to a borrower in Jakarta or Istanbul has quietly gotten much worse.
This is the part that trips people up. The Fed can hold its own policy steady, the domestic aggregates can look fine, and offshore dollars can still be draining out from under everyone. The Fed influences the offshore system, mostly through the price of the dollars that anchor everything and through the swap lines it extends to a handful of other central banks in a crisis. But influence is not control. Nobody has a clean dashboard for the total stock of eurodollars because a huge share of it is interbank, cross-border, and off the kind of balance sheet that gets reported cleanly. You are always estimating.
The proxies I actually watch
Since you cannot see the eurodollar supply directly, you read it through proxies. These are the observable signs that dollars are getting harder to source outside the US, and they tend to move together when something is genuinely wrong. None of them is perfect on its own. The point is convergence. When several of them stress at once, that is the signal.
- The broad dollar index. A rising dollar against a basket of currencies is the crudest proxy for offshore dollar scarcity. When dollars are hard to get, their price goes up. A slow grind higher is different from a fast spike, and the fast spike is the one that hurts borrowers who owe in dollars but earn in something else.
- Cross-currency basis swaps. This is the most direct read I know of. It measures how much extra a foreign institution has to pay to borrow dollars through the swap market versus what interest rate parity says it should cost. When that basis blows out negative, it means someone is paying a premium just to get dollars, which is textbook offshore tightness.
- Front-end funding spreads. The gap between what banks charge each other for short-term dollars and the risk-free rate widens when banks stop trusting each other with overnight cash. It is a domestic-flavored measure but it bleeds straight into the offshore system.
- Emerging market currencies as a group. Not one currency, the whole cohort. When the lira, the rand, the real, and a handful of Asian currencies all weaken against the dollar together, that is rarely a local story. That is dollars leaving.
My rule of thumb is that any single one of these can move for boring reasons. Two of them moving together gets my attention. Three or four at once, especially if the basis is blowing out, and I treat it as a funding event whether or not anyone has called it that yet.
Why crypto and emerging markets take the hit together
Here is the connection that matters for anyone holding risk. A eurodollar squeeze is, at its core, a shortage of dollars for people who owe dollars and hold something else. When that shortage bites, those people have to sell the something else to raise dollars. Emerging market assets get sold because a lot of that borrowing funded emerging market exposure in the first place. And crypto gets sold for the same mechanical reason it always does under stress, which is that it is liquid, it trades around the clock, and it is easy to dump when you need cash right now and the traditional markets are closed or thin.
So the two are not correlated because one causes the other. They are correlated because they share a funding source. When offshore dollars get scarce, the most liquid risk assets on the planet all become sources of cash at the same moment, and crypto is near the top of that list. This is why a crypto drawdown can arrive with no crypto-specific news at all. The news was in a swap market you were not watching.
The practical failure mode I have watched people fall into is treating a funding-driven selloff like a fundamental one. They see their crypto or their emerging market position drop, they go hunting for a token-specific or country-specific reason, they find some plausible narrative, and they either panic sell into the hole or double down on a story that was never the actual driver. Meanwhile the real driver was global dollar tightness that has nothing to do with the asset and everything to do with who owes dollars to whom.
How to actually use this
You do not need to model the eurodollar system to benefit from knowing it exists. What you need is a short pre-flight check before you decide what a selloff means. When a risk position of yours is falling, before you reach for the asset-specific explanation, glance at the dollar, the cross-currency basis if you can get it, and the emerging market currency cohort. If those are all quiet, the move is probably about the asset and you can reason about it normally. If those are stressed, you are likely inside a dollar funding event, and the correct read is that a lot of unrelated things are going to fall together for a while and then mean-revert when dollars loosen up again.
I want to be honest that this is a lens, not a timing tool. The proxies tell you the character of a move, not its exact top or bottom, and the eurodollar system is opaque enough that anyone claiming precision about its total size is guessing. What it buys you is the ability to stop assigning a fundamental story to what is really a plumbing story. That alone has kept me from a few bad decisions, which is about as much as I ask from any single framework.