JPMorgan and Bank of America are warning investors—but here's what's key to Q4 earnings

JPMorgan and Bank of America are warning investors that trading revenues for the fourth quarter will be down about 15% compared to last year. We’ve seen the banks get a lift recently from tax cut news. What should investors expect for the big banks this quarter? Yahoo Finance's Alexis Christoforous and Jared Blikre discuss.