The biggest question facing the economy lately has been: How bad will the banking turmoil be? Though two U.S. banks failed a month ago, and a third is still struggling, emergency lending by the Federal Reserve seems to have prevented broader harm, according to a Wall Street Journal commentary. The next question should be: Will it spread beyond the banks? That is because the collapse of Silicon Valley Bank a month ago, which touched off this bout of turmoil, was a symptom, not a cause, of broader forces at work in the financial system and the economy. SVB’s core problem was that it owned a lot of government debt funded by unstable deposits. As interest rates rose sharply last year, the mark-to-market value of that debt plummeted, and deposits became more expensive and scarcer. A lot of banks own similarly devalued bonds. But that is just the tip of a debt iceberg. Since the end of 2009, total debt owed by governments, businesses and households has risen 90% to $68 trillion, according to the Federal Reserve.