How Margin Debt Works

Margin debt is a sometimes-overlooked but key part of the stock market that is particularly pertinent right now.

It is the money that investors borrow from stockbrokers to buy securities when they can’t or don’t want to fund the entire purchase with cash. Say an investor wants to purchase 100 shares at $50 each for a total of $5,000 but has only $2,500 to invest. That individual could buy the rest of the shares on margin. The same process can be used to buy exchange-traded funds.

Investors frequently use margin to get more bang for their investing buck. “The pro of margin is that it increases your purchasing power,” says Jeff Deiss, director of wealth planning at ACM in Ridgewood, N.J.

The downside is that brokers typically charge interest on borrowed money. And if the individual starts losing money on the investment, the stockbroker might ask for additional cash as security or collateral. That decision and how much cash will be required will depend on a variety of factors, including the remaining value of the investment, how much money the investor owes the broker and the requirements of the broker.

“Buying on margin comes with a lot of risk, and if you are going to use margin, it is probably a good idea to have some cash on the side,” says Mr. Deiss. Investors who don’t have the required additional cash may be forced to close out their positions at a loss.

A large amount of buying on margin also can be detrimental to the stock market as a whole.

At the end of January, customer margin debt at U.S. brokers regulated by the Financial Industry Regulatory Authority, or Finra, jumped to $799 billion from $562 billion a year earlier, according to data provided by Finra.

Some analysts say that jump in margin debt came from individual investors, who turned to online trading amid pandemic-related lockdowns. A combination of new easy-to-use trading technology, ultralow borrowing costs and stimulus checks from the federal government helped fuel the phenomenon.

“For younger folks, it’s kind of the drug of choice,” Mr. Deiss says.

The problem is, when there is a lot of margin debt concentrated in a few stocks, those stocks tend to see wild price swings, says Fabiana Fedeli, global head of fundamental equities at Rotterdam-based asset-management company Robeco. Anecdotal evidence indicates that the recent increase in margin debt coincided with higher participation levels by individual investors, she says.

Indeed, certain stocks that became popular with individual investors also saw price volatility earlier this year. “The minute that the margin couldn’t be met, some of the positions had to be sold immediately,” Ms. Fedeli says. “It gives volatility to the market,” she says.