While a flood of merger and acquisition activity will eventually be a boon for the biggest US investment banks, the last 18 trading days of September are more important for their earnings in the near term.

Since August 1, Goldman Sachs and Morgan Stanley have picked up lots of advisory business on a surge in announced mergers and acquisitions. Excluding spin-offs, as of yesterday, Goldman advised on deals valued at roughly $96bn (€75bn) in August, while Morgan Stanley advised on about $49bn in deals, according to Dealogic.