As the calendar turns for the biggest banks, a big question mark looms: Where will growth come from next year?

A major feature of the global Wall Street banks is the diversity of their revenue sources. They don’t just make money from lending and deposits, like many regional banks, but also via trading and corporate advisory fees. And while volatile interest rates are known to scare chief executives and corporate boards from making big acquisition moves, they can sometimes be a big boost for trading desks.