Index and Margin for Adjustable-Rate Mortgage

The interest of adjustable-rate mortgages (ARM) are tied to the index and margin. The index is a reference point for the interest rate and will vary based on the market. The margin, on the other hand, is a firm set of percentage points that the lender determines. When added together, a new interest rate for the loan is established. Ultimately, this will affect how much borrowers will pay every month for the loan.