The bank's net interest margin--the difference between its cost of capital and average loan rate--has fallen for five consecutive quarters, to 0.9%.

FORBES: After the bubble

The high net interest margins at Wells Fargo have, in large part, been attributed to its large low cost average core deposits (which include noninterest-bearing deposits, interest-bearing checking, savings certificates, market rate and other savings, and certain foreign deposits).

FORBES: Three Ways To Tell If Pain Or Pleasure Ahead For Wells Fargo