Margin Debt Risk: The Ratios That Mislead Investors

key takeaways margin debt

Margin debt just set another record. In May 2026, investors owed their brokers a combined $1.42 trillion, the highest in history and a 53.7% jump from the prior year.1 Every time this number prints a new high, the same charts circulate: margin debt against GDP, against M2, against the total value of the market. They look authoritative. The trouble is that most of them can’t measure margin debt risk in any way that helps you manage a portfolio, and the most popular one is the least useful of the bunch.

I want to take these apart in order.

  1. Why do the three favorite ratios misstate margin debt risk?
  2. Then the handful of measures that actually tell you something.
  3. Finally, I will build a cleaner gauge out of the defensible pieces, and close with the part that matters most: what to watch, and why leverage is a problem you can ignore right up until the week you can’t.

However, before that, let’s discuss a little background.

Why Margin Debt Risk is back in the Conversation

The recent surge in the market has certainly concerned some corners of the investing world. Stocks have run hard, confidence is high, and borrowing against portfolios has exploded. Margin debt crossed $1 trillion for the first time in mid-2025 and hasn’t looked back, climbing 8.5% in May alone.1 As I wrote earlier this year in Margin Debt Sets Records: Should We Be Concerned?, leverage tends to peak right alongside the market because the same euphoria drives both.

However, here is the mechanism that many people get wrong. They assume margin debt drives prices higher, that borrowed money is the fuel under the rally. In aggregate, that channel is small because reported margin debt is only about 2% of total market value.

The dominant arrow runs the other way. Rising prices increase the value of collateral in every margin account, which automatically increases how much each investor can borrow under Reg T. Debt rises BECAUSE the market rose, not the reverse. That single fact is what breaks the ratios we’re about to examine, and it lies at the core of why margin debt risk is so often misjudged.

Okay, so let’s get into the misleading ratios that are popular on the “interwebs.”

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