Debt traders at Goldman Sachs Group Inc. stumbled badly in the last quarter of 2017, generating just $1 billion of revenue. Back in 2009, they brought in that much every 10 days.

Reporting its fourth-quarter results Wednesday, Goldman said debt-trading revenue fell 50%—the worst three-month showing since 2008 and the latest in a nearly unbroken chain of quarterly declines in the business.

The numbers reflect problems not unique to Goldman, whose struggles have been acute, but also a wider malaise that has settled over Wall Street’s securities operations, once the source of fat profits.

The trouble isn’t rogue traders or big bets gone bad, but shrinking demand from investors who, with little conviction about how to play the markets, simply sit it out or opt for cheap, off-the-shelf investment products, such as index funds.

Meanwhile, new regulations have cast banks as mere toll-takers, and more transparent and accessible data have eroded the informational edge that once gave them pricing power over their clients.