The bank interest margin, i.e., the spread between the loan rate and the deposit rate, is one of the principal elements of bank net cash flows and after-tax earnings and is often used as a proxy for the efficiency of financial efficiency. Little attention has been paid to the effects of administrative cost denoted by personal expense on bank equity returns and risks since the use of administrative cost as a strategy is much less widely accepted than is often believed by widening its interest margin and thus decreasing its risk in equity return.