Net Interest Margin

What Does Net Interest Margin Mean?
A performance metric that examines how successful a firm's investment decisions are compared to its debt situations. A negative value denotes that the firm did not make an optimal decision, because interest expenses were greater than the amount of returns generated by investments.

Calculated as:

Investopedia explains Net Interest Margin
For example, ABC Corp has a return on investment of $1,000,000, an interest expense of $2,000,000 and average earning assets of $10,000,000. ABC Corp's net interest margin would be -10%. This would mean that ABC Corp has lost more money due to interest expenses than was earned from investments. In this case, ABC Corp would have been better off if it had used the investment funds to pay off debts instead to making an investment.