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The Pros and Cons of COFI ARMs

by Arnold Kling
November 8, 1994

In the 1980's, some California savings and loan institutions came up with the idea of an adjustable-rate mortgage whose interest rate would float up and down with the average interest rate paid on deposits in their area. That way, the interest rate spread between their mortgage assets and their deposit liabilities would be stable.

To measure their average deposit rate costs, these California thrifts used the "11th district Cost Of Funds Index," or COFI. The "11th district" refers to the Federal Home Loan Bank System's western region, which consists primarily of California.

What is distinctive about COFI ARMs?

When a prospective borrower first hears about a COFI ARM, he or she often will ask, "Is COFI a good index or a bad index for me?" In fact, over periods of a year or longer, all interest rate indices tend to move together. There probably is no such thing as a "good" index or a "bad" index. The COFI index tends to move a bit more slowly than other indices, which is good for you if rates are rising but not good for you if rates are falling. (You can see this behavior in the data table we set up to compare COFI with the 1-year and 3-year Treasury indexes.) However, the impact of this sluggishness on the performance of your ARM is much less than the impact of other features of the ARM.

In fact, what is distinctive about COFI ARMs is not the index per se, but the creativity that lenders have used in designing COFI ARM products. Historically, the ARM products tied to indexes of Treasury rates have been relatively standard, while those tied to COFI or LIBOR (another index, that I will not get into here) have shown more variety.

What the greater variety means to you as a borrower is that there are more opportunities to get a COFI ARM deal that is particularly good--or particularly bad. You have to scrutinize the characteristics carefully.

The characteristics to watch for

If I told you that you could get a COFI ARM for 3-7/8 percent, in today's environment where Treasury ARM start rates are close to 6 percent, you might get pretty excited. However, what if I told you that this particular COFI ARM has no rate cap, and that it adjusts after just three months? That means that in three months your rate could be 9 percent or higher, while with a one-year Treasury ARM your rate would still be at 6 percent, most likely with a cap of 8 percent in the second year.

Questions to ask about any ARM product, not just COFI, include:

Loans without rate caps

One of the more creative designs of COFI ARMs uses a payment cap instead of an interest rate cap. This increases the borrower's financial risk.

Suppose that your ARM starts at 5 percent and adjusts after six months, at which time the formula says that the rate should be 7.5 percent. If you had an interest rate cap which said that the rate could not adjust more than 1 percent every six months, then you would have only a 6 percent rate.

With a payment-capped ARM under the same scenario, the good news is that your monthly payment does not change after 6 months. The bad news is that the interest rate adjusts fully to 7.5 percent. How can this work?

When your interest rate goes up but your payment stays the same, more of your monthly payment goes to interest and less goes to bring down the principal balance of the loan. In fact, it is very likely that your monthly payment will not even be enough to cover the interest, and the interest shortfall will be added to your outstanding balance. In other words, the outstanding balance on your loan will increase during the period when the payment cap is binding.

Do many people take COFI ARMs?

Over the years, hundreds of thousands of borrowers have taken out mortgages linked to COFI, and most of them are satisfied. Some of the best deals in the market today are for COFI ARMs, because many lenders believe that an index that moves with their cost of funds reduces their risk, . However, because some of the COFI products do not offer rate caps or other key features to protect the borrower, you need to be particularly careful to study the product before you make your choice.


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