The APR may be below the initial interest rate on an ARM if the index plus margin when the loan is made is below the initial rate. This is unusual, most of the time the initial rate is below the index plus margin, but it did happen in 2003-4.

Annual Percentage Rate (APR) Below Interest Rate on ARMs?
May 5, 2003, Revised November 10, 2006, January 3, 2008, August 20, 2010, Reviewed February 5, 2011

The APR may be below the initial interest rate on an ARM if the fully indexed rate, which is the sum of the current value of the rate index when the loan is made, plus the margin, is below the initial rate. This is unusual, most of the time the initial rate is below the index plus margin, but it did happen in 2003-4. This article can be viewed as a companion piece to Annual Percentage Rate (APR) Below Interest Rate on FRMs?

The APR Calculation on an ARM


"I’m considering a 3/1 ARM and am confused about the APR on this loan. I thought that when there were lender fees, the APR would be above the interest rate. But this 3 /1 ARM has lender fees, yet the APR is below the interest rate. Is this lender making a mistake?"

No. On an ARM, the quoted interest rate holds only for a specified period, which can range from a month to 10 years. In calculating an APR, therefore, some assumption must be made about what happens to the rate at the end of the initial rate period. If the assumption is that the rate will decline at the end of the initial rate period, the APR will be below the initial rate unless offset by high lender fees.

ARMs first burst on the scene in the early 80s, a period of very high interest rates. In calculating the APR on an ARM at that time, it was assumed that the initial rate lasted through the life of the loan. This led to absurdly low APRs on ARMs with low "teaser" rates that held for only a short period – in some cases, for only a month.

So the Federal Reserve, which administers Truth in Lending, changed the rule for calculating the APR on an ARM. It said that the APR calculation should use the initial rate only for as long as it lasted, and then should use the rate that would occur if the interest rate index used by the ARM stayed the same for the life of the loan. This is called a "no-change" or "stable- rate" scenario.

Under a stable-rate scenario, at the end of the initial rate period, the interest rate used in calculating the APR adjusts to equal the "fully-indexed rate", or FIR. The FIR is the value of the interest rate index at the time the ARM was written, plus a margin that is specified in the note.

Assuming zero loan fees , the APR on an ARM will be below the interest rate if the FIR is below the interest rate, and vice versa.

Some Illustrations


The indexes used by ARMs are short-term rates. A common one is the one-year Treasury rate, which I will use in my illustrations. In April, 1995, that rate was about 6.25%, in April 2003, it was down to about 1.25%, and in November, 2006 it had climbed back to about 5%.

An ARM that uses this index, say a 5 /1 on which the initial rate holds for 5 years, might have a margin of 2.75%. The initial rate would change over time but much less than the index it uses, as shown below.

Month Initial ARM Rate One Year Index Fully Indexed Rate APR With Zero Fees
April 1995 7% 6.25% 9.00% 8.15%
April 2003 5% 1.25% 4% 4.36%
November 2006 6% 5.00% 7.75% 7.04%
August 2010 3% 1.00% 3.75 3.49%


Thus, in 1995, 2006 and 2010, the FIR was higher than the initial ARM rate, which meant that the APR was higher at zero fees. In 2003, the opposite was the case.

Implications For ARM Borrowers


A FIR above the initial rate is often viewed as the norm. It is the origin of the term "teaser", which means a rate below the FIR. To the borrower, it means that if the market stays where it is, the rate will increase at the first adjustment. Canny borrowers who are alert to this may plan to refinance at that time and receive another teaser.

A FIR below the initial rate means that if the market stays where it is, the rate will drop at the first rate adjustment. This makes ARMs more attractive, because of the high likelihood that the borrower will enjoy a rate drop without having to refinance. 
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