Maybe the massive U.S. repo market isn’t as massive as we thought. That’s the conclusion of a study by researchers at the Federal Reserve Bank of New York that suggests transactions in the repurchase agreement (repo) market total about $5.48 trillion. The figure, though impressive, is a far cry from a previous and oft-cited $10 trillion estimate made in 2010 by two Yale professors, Gary Gorton and Andrew Metrick. The Fed researchers, acknowledging the “spotty data” that complicates such tasks, argue the previous $10-trillion estimate is based on repo activity in 2008 when the market was far larger, and is inflated by double-counting.

Repos are a key source of collateralized funding for dealers and others in financial markets, and represent a main pillar of the “shadow” banking system. The market was central to the downfalls of Lehman Brothers and Bear Stearns in the 2008 crisis, and now regulators from Fed Chairman Ben Bernanke on down are looking for a fix. Earlier this year, the New York Fed itself said it might restrict the types of collateral in so-called tri-party repos, after being dissatisfied with progress by an industry committee.

The study published by the New York Fed on Monday slices the complex market into five segments, mapping the flow of cash and securities among dealers, funds and other players. Because dealers represent about 90 percent of the tri-party market, the Fed study extrapolates that onto the broader repo market, to arrive at its estimates. Bottom lines: U.S. repo transactions total $3.04 trillion; U.S. reverse repo transactions total $2.45 trillion.