FORTUNE -- Call it too big to succeed.
A report about the global banking industry by Boston Consulting Group, which was released on Tuesday, says new regulations and less business will force the big banks to dramatically shrink. Of the 28 global banks the consulting firm looked at, only a few of the leading players like -- Goldman Sachs (GS), Deutsche Bank (DB), and JPMorgan Chase (JPM) -- will be able to remain at their current size, according to BCG.
The others, which include such banking behemoths as Bank of America (BAC), Barclays (BCS), Citigroup (C), Credit Suisse (CS), and Morgan Stanley (MS), will have to exit businesses, eliminate staffers, and rethink what they do in order to survive.
Even so, BCG estimates the leading players still need to cut costs relative to income by 10% in order to hit profit targets. If profits don't increase, and cuts are spread evenly, that alone could mean an additional 40,000 in layoffs from the largest banks. For all the banks, BCG sees little in the way of revenue growth in the next year or so.