Adjustable Rate Mortgage

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Adjustable Rate Mortgage

A mortgage with an interest rate that changes periodically. Generally speaking, an adjustable rate mortgage is linked to some major benchmark rate; for example, the interest rate may be stated as "LIBOR + 1%." The mortgage may or may not have a cap on how much the interest rate can rise or fall, or on how often the interest rate may change. Very often, the initial interest rate for an adjustable-rate mortgage is lower than that for a fixed-rate mortgage. This allows more people to qualify for an adjustable-rate mortgage; however, this kind of mortgage can be risky because the interest rate (and therefore the monthly payment) can rise unexpectedly. Indeed the prevalence of ARMs has been blamed for the housing bubble in the mid-2000s and the subsequent recession. See also: Credit Crunch, Teaser Rate.
Farlex Financial Dictionary. © 2012 Farlex, Inc. All Rights Reserved

Adjustable rate mortgage (ARM).

An adjustable rate mortgage is a long-term loan you use to finance a real estate purchase, typically a home.

Unlike a fixed-rate mortgage, where the interest rate remains the same for the term of the loan, the interest rate on an ARM is adjusted, or changed, during its term.

The initial rate on an ARM is usually lower than the rate on a fixed-rate mortgage for the same term, which means it may be easier to qualify for an ARM. You take the risk, however, that interest rates may rise, increasing the cost of your mortgage. Of course, it's also possible that the rates may drop, decreasing your payments.

The rate adjustments, which are based on changes in one of the publicly reported indexes that reflect market rates, occur at preset times, usually once a year but sometimes less often. Typically, rate changes on ARMs are capped both annually and over the term of the loan, which helps protect you in the case of a rapid or sustained increase in market rates.

However, certain ARMs allow negative amortization, which means additional interest could accumulate on the outstanding balance if market rates rise higher than the cap. That interest would be due when the loan matured or if you want to prepay.

Dictionary of Financial Terms. Copyright © 2008 Lightbulb Press, Inc. All Rights Reserved.

Adjustable Rate Mortgage (ARM)

A mortgage on which the interest rate can be changed by the lender.

While ARM contracts in many countries abroad allow rate changes at the lender's discretion (Discretionary ARMs), in the U.S. rate changes on ARMs are mechanical. They are based on changes in an interest rate index over which the lender has no control. Henceforth, all references are to such Indexed ARMs.

Reasons for Selecting an ARM: Borrowers may select an ARM in preference to a fixed rate mortgage (FRM) for three reasons:

• To qualify: they need an ARM to qualify for the loan they want.

• To take advantage of low initial rates on ARMs and their own short time horizon: they expect to be out of their house before
    the initial rate period ends.

• To gamble on future interest rates: they expect that they will pay less on the ARM over the life of the loan and are prepared     to take the risk that rising interest rates will cause them to pay more.

I will return to these reasons later.

How the Interest Rate on an ARM Is Determined: There are two phases in the life of an ARM. During the first phase, the interest rate is fixed, just as it is on an FRM. The difference is that on an FRM the rate is fixed for the term of the loan, whereas on an ARM it is fixed for a shorter period. The period ranges from one month to 10 years.

At the end of the initial rate period, the ARM rate is adjusted. The adjustment rule is that the new rate will equal the most recent value of a specified interest rate index, plus a margin. For example, if the index is 5% when the initial rate period ends, and the margin is 2.75%, the new rate will be 7.75%. The rule, however, is subject to two conditions.

The first condition is that the increase from the previous rate cannot exceed any rate adjustment cap specified in the ARM contract. An adjustment cap, usually 1% or 2% but ranging in some cases up to 5%, limits the size of any interest rate change.

The second condition is that the new rate cannot exceed the contractual maximum rate. Maximum rates are usually five or six percentage points above the initial rate.

During the second phase of an ARM's life, the interest rate is adjusted periodically. This period may or may not be the same as the initial rate period. For example, an ARM with an initial rate period of five years might adjust annually or monthly after the five-year period ends.

The Quoted Interest Rate: The rate that is quoted on an ARM, by the media and by loan providers, is the initial rate—regardless of how long that rate lasts. When the initial rate period is short, the quoted rate is a poor indication of interest cost to the borrower. The only significance of the initial rate on a monthly ARM, for example, is that this rate may be used to calculate the initial payment. See How the Monthly Payment on an ARM Is Determined.

The Fully Indexed Rate: The index plus margin is called the “fully indexed rate,” or FIR. The FIR based on the most recent value of the index at the time the loan is taken out indicates where the ARM rate may go when the initial rate period ends. If the index rate does not change, the FIR will become the ARM rate.

For example, assume the initial rate is 4% for one year, the fully indexed rate is 7%, and the rate adjusts every year subject to a 1% rate increase cap. If the index value remains the same, the 7% FIR will be reached at the end of the third year.

The FIR is thus an important piece of information, the more so the shorter the initial rate period. Nevertheless, it is not a mandated disclosure and loan officers may not have it. They will know the margin and the specific index, however, and the most recent value of the index can be found on the Internet, as explained below.

ARM Rate Indexes: Every ARM is tied to an interest rate index. An index has three relevant features:

• Availability
• Level
• Volatility

All the common ARM indexes are readily available from a published source, with the exception of one called the Cost of Savings Index, or COSI. I would avoid it.

In principle, a lower index is better for a borrower than a higher one. However, lenders take account of different index levels in setting the margin. A3% index with a 2% margin provides the same FIR as a 2% index with a 3% margin. Assuming volatility is the same, there is nothing to choose between them.

An index that is relatively stable is better for the borrower than one that is volatile. The stable index will increase less in a rising rate environment. While it will also decline less in a declining rate environment, borrowers can take advantage of declining rates by refinancing.

The most stable of the more widely-used rate indexes is the 11th District Cost of Funds Index, referred to as COFI (not “coffee”). Most of the others are significantly more volatile. These include the Treasury series of constant (one-, two-, or three-year) maturity, one-month and six-month Libor, six-month CDs and the Prime Rate.

Another series known as MTA is a 12-month moving average of the one-year Treasury constant maturity series. MTA is a little more volatile than COFI but less volatile than the other series.

An ARM should never be selected based on the index alone. That would be like buying a car based on the tires. But if an overall evaluation (see below) indicates that two ARMs are very close, preference could be given to the one with the more stable index.

Current and historical values of major ARM indexes can be found on  the  following  Web  sites:,,, and

How the Monthly Payment on an ARM Is Determined: ARMs fall into two major groups that differ in the way in which the monthly payment of principal and interest is determined: fully amortizing ARMs and negative amortization ARMs.

Fully Amortizing ARMs adjust the monthly payment to be fully amortizing whenever the interest rate changes. The new payment will pay off the loan over the period remaining to term if the interest rate stays the same.

For example, a $100,000 30-year ARM has an initial rate of 5%, which holds for five years, after which the rate is adjusted every
year. (This is referred to as a “5/1 ARM.”) The payment of $536.83 for the first five years would pay off the loan if the rate stayed at 5%. In month 61, the rate might increase to, say, 7%. A new payment of $649.03 is then calculated, at 7% and 25 years, which would pay off the loan if the rate stayed at 7%. As the rate changes each year thereafter, a new payment is calculated that would pay off the loan over the remaining period if that rate continued.

Negative Amortization ARMs allow payments that don't fully cover the interest. They have one or more of the following features:

Payment Rate Below the Interest Rate: The payment rate, which is the interest rate used to calculate the payment, may be below the actual interest rate. If the payment rate is so low that the initial payment does not cover the interest, the result will be negative amortization.

More Frequent Rate Adjustments than Payment Adjustments: If, e.g., the rate adjusts every month but the payment adjusts every year, a large rate increase within the year will lead to negative amortization.

Payment Adjustment Caps: If a rate change is large and a payment adjustment cap limits the size of a change in pay-
    ment, the result will be negative amortization.

Virtually all ARMs are designed to fully amortize over their term. This means that negative amortization can only be temporary and at some point or points in the ARM's life history the monthly payment must become fully amortizing.

Two contract provisions are used to assure that negative amortization ARMs pay off at term.
• Arecast clause requires that periodically, usually every five years, the payment must be adjusted to the fully amortizing
• Anegative amortization cap is a maximum ratio of loan balance to original loan amount, for example, 110%. If that maximum is reached, the payment is immediately adjusted to the fully amortizing level, overriding any payment adjustment cap. In a worse case scenario, the required payment increase may be very large.

Identifying ARMs: There are no industry standards for identifying ARMs and practices vary across lenders. Some identify their ARMs by the index used, e.g., “COFI ARM” or “six-month Libor ARM.”
Some identify their ARMs by the rate adjustment periods, e.g., “5/1” or “3/3.”
None of these shorthand descriptions are of much use to borrowers because there are so many differences within each. Indeed, even if the features of each were standardized, to compare one type of ARM with another, one needs to know exactly what those features are.

Selecting an ARM to Qualify: It is easier to qualify with an ARM than with an FRM. In deciding whether an applicant has enough income to meet the monthly payment obligation, lenders usually use the initial interest rate on an ARM to calculate the payment, even though the rate may rise at the end of the initial rate period.

That's why, when market interest rates increase, ARMs become more common and FRMs less common. Some borrowers who could have qualified with an FRM at the lower rates, now require an ARM to qualify.

However, many borrowers who appear to require an ARM to qualify in fact could qualify with an FRM. It just takes a little more work. See Qualification/Meeting Income Requirements/Is an ARM Need to Qualify?

Taking Advantage of Low Initial Rates: Borrowers with short time horizons can take advantage of the initial interest rates that are lower on ARMs than on FRMs. For example, at a time when a borrower is quoted 6.5% on a 30-year FRM, the quoted initial rates on 3/1, 5/1, 7/1, and 10/1 ARMs might be 6%, 6.125%, 6.25%, and 6.375%, respectively.

The correct choice depends on how long the borrower expects to have the loan and on the borrower's attitude to risk. For example, a borrower who expects to hold the mortgage for six years might play it safe by selecting a 7/1. Or, he might take the 5/1 on the grounds that the savings over five years justifies taking the risk of having to pay a higher rate in year six.

Borrowers who take this risk, whether deliberately as in the example above, or inadvertently because they aren't sure how long they will hold the loan, should consider what can happen at the end of the initial rate period. Suppose the borrower deciding between the 5/1 and 7/1, for example, finds that the indexes, margins, and maximum rates are the same, but the rate adjustment caps are 2% on the 5/1 and 5% on the 7/1. This could tilt the decision toward the 5/1.
    If the ARMs being compared differ in a number of ways, however, comparing one with another (or with an FRM) can be very confusing. In this situation, borrowers with short time horizons seeking to take advantage of low initial rates on ARMs are no different than borrowers with longer horizons who seek to pay less on the ARM over the life of the loan and are prepared to take the risk that they will pay more. Both should analyze the potential benefits and risks with calculators, as explained below.

Gambling on Future Interest Rates:Taking an ARM (when an FRM is an option) is a gamble, and the question is whether it is a good gamble in any particular case. A good gamble is one where the borrower can reasonably expect that the Interest Cost (IC) will be lower on the ARM than on a comparable FRM over the period the mortgage is held; and where the borrower won't face extreme hardship if interest rates explode.

There are four calculators on my Web site designed to deal with these issues. Two of them, 9a) and 9b), show IC over periods speciied by the user. Two others, 7c) and 7d), show mortgage payments month by month. For both IC and payments, one calculator is for ARMs that allow negative amortization and one is for ARMs that don't.

Information Needed: All the calculators require the following information about each ARM:
Basic Loan Information
• New loan amount or existing loan balance (e.g., 100,000)
• Initial interest rate on new loan or current rate on existing loan (e.g., 7.50)
• New loan term or remaining term on existing loan, in months (e.g., 360)
Interest Rate Index
• Selected index, e.g., 11th district cost of funds or “COFI”
• Margin that is added to interest rate index (e.g., 2.75)
First Rate Adjustment
• Number of months to first rate adjustment (e.g,. 36)
• Maximum interest rate change on first rate adjustment (e.g., 5.0)
Subsequent Rate Adjustments
• Duration, in months, between subsequent rate adjustments (e.g., 12)
• Maximum interest rate change on subsequent rate adjustments (e.g., 2.0)
Maximum/Minimum Rates
• Maximum interest rate over life of mortgage (e.g., 12.5)
• Minimum interest rate over life of mortgage (e.g., 4.5)
On negative amortization ARMs, the following is also needed:
Payment Information
• Initial monthly payment of principal and interest (e.g., 753.45)
• Payment adjustment period, in months (e.g., 12)
• Payment adjustment cap, in percent (e.g., 7.5)
• Payment recast period, in years (e.g., 5)
• Negative amortization cap, in percent (e.g., 110)
The calculators directed to IC will ask for additional information needed to calculate IC. This includes the user's tax bracket, down payment, points, and other upfront fees.
Assumptions About Future Interest Rates
• Stable index: interest rate index stays unchanged for the life of the mortgage
• Worst case: ARM rate rises to the maximum extent permitted by the loan contract

of years
per year
• Rising trend: interest rate
index rises:
• Declining trend: interest rate
index falls:
  Years between
direction changes
per year
• Volatile: interest rate index
• Volatile: interest rate index

Note: the above numbers are illustrative.

The stable index or “no-change” scenario provides the closest approximation to an “expected” result and is an excellent benchmark. The worst case is exactly that—the ARM rate rises as far and as fast as the loan contract permits. The worst case is so improbable that borrowers may want to design something less extreme, such as the rising trend scenario used below where the index rises by 1% a year for five years.

An illustration: On July 25, 2002, I used the calculators to compare the six-month fully amortizing ARM and the FRM shown below.

Mortgage FeaturesFRMARM
Term30 Years30 Years
Initial Interest Rate6.375%3.5%
Index Value1.81%
Rate Adjustment Period6 months
Rate Adjustment Cap1%
Maximum Rate11%

Using the interest cost calculator for fully amortizing ARMs (9a), I developed the following table.

Interest Cost on ARM and FRM, July 25, 2002
FRM6-Month Libor ARM
PeriodStable RatesRising TrendWorst Case
3 Years6.56%3.99%5.20%6.45%
5 Years6.503.795.907.84
7 Years6.473.706.488.53
12 Years6.443.617.069.20
30 Years6.423.567.399.57

The appeal of the ARM at that time is evident. In a stable rate environment, the borrower would save more than 2.5% relative to the FRM. In a rising trend environment, the ARM would cost less than the FRM if the borrower is out in five years, and even in a worst case the ARM is better if the borrower is out in three years.

For many consumers, the bottom line is what might happen to the payment. Using the payment calculator for fully amortizing ARMs (7b), I developed the table below. The scenarios are the same and the loan is assumed to be $300,000.

Mortgage Payment on a $300,000 ARM and FRM
FRM6-Month Libor ARM
MonthsStable RatesRising TrendWorst Case
37-42 1,858 2,471
43-48 1,949 2,676
49-54 2,040 2,780
55-60 2,132
61-66 2,224

The payment increases on the six-month Libor ARM under a worst-case scenario are substantial but spread out over four years.
None of the increases exceed 13%. There are other ARMs in which the payment under a worst case can jump 50% or more at one adjustment. This is sometimes referred to as “payment shock.”

Mandatory Disclosures: The theory underlying the Federal Reserve's disclosure rules for ARMs is that consumers should first receive a general education on ARMs and then should receive specific information about any ARM program in which they might be interested. This is a reasonable approach.

The general education is provided by a Consumer Handbook on Adjustable Rate Mortgages, sometimes referred to as the “Charm Booklet.” The booklet is a passable effort, but it is too long so few people read it.

The second part of ARM disclosure is a list of ARM features that must be disclosed and an explanation of, “each variable-rate program in which the consumer expresses an interest.” This is where the process breaks down. The list of ARM features is too long and includes all kinds of pap.

Overwhelming borrowers with more information than they can handle is counter-productive. Disclosing everything is much the same as disclosing nothing, it just takes longer.

Government agencies with responsibility for disclosure are extremely reluctant to recognize this. If they did, they would be
obliged to determine what was truly important. They could no longer compromise divergent views about what to include by
including everything. Even worse, they could no longer ignore mandated disclosures from other agencies that hit the borrower at about the same time.

Lenders don't make this mistake. They know they can't sell an ARM (or anything else) by overwhelming the customer. They tend to focus on a single theme or hook—an easy to understand ARM feature that is appealing. For example, in 2003 they sold COFI ARMs based on the stability of the COFI index and Libor ARMs based on a very low initial rate index.

ARM disclosures would be a useful counterweight to lender sales pitches if they were limited to critically important information and
presented clearly. The most critical information for most borrowers is 1) What would happen to the interest cost on the loan and the monthly payment per $100,000 of loan amount, if the interest rate index doesn't change; and 2) What would happen if the loan rate rises to the maximum permitted by the loan contract? Simple and easy to understand tables for displaying this information were shown above.

Instead, borrowers are presented with a list of ARM features, including those needed to derive useful tables, provided that the
borrower knows a) which items are relevant and b) how to derive the tables from them. But such borrowers don't need mandatory disclosure; they can get the information they want by asking for it. Mandatory disclosure is for borrowers who don't know what they need and, therefore, don't know what to look for in voluminous disclosures.

In addition to the list of ARM features, lenders are required to describe each program, but there is no requirement for clarity. So long as the mandated items are included, it seemingly doesn't matter whether the descriptions are comprehensible. I have seen a few that are pretty good, but most are unreadable.

Convertible ARMs: Some ARMs have an option to convert to an FRM after some period, at a market rate. The advantage, relative to a refinance, is that the conversion avoids settlement costs. The disadvantage is that the borrower loses the flexibility to shop the market.

The conversion interest rate on the FRM is usually defined in terms of the value of a rate index at the time of conversion, plus a margin. To determine whether the conversion option has value, assume you can convert immediately. Find the current index value, add the margin and compare it to the best FRM rate you can obtain in the market. If the second rate is lower, which is likely to be the case, the conversion option has little value.

Market conditions do change and it is possible that the option could have value in the years ahead. But don't give up anything important for it.

Also see: Points/Paying Points on an ARM, Partial Prepayments/Effect of Early Payment on Monthly Payments/ARMs, Qualification/Meeting Income Requirements/Is an ARM Needed to Qualify?, Interest-Only Mortgage/Interest-Only ARMs, Second Mortgages/Negative Amortization ARM May Prevent a Second Mortgage.

The Mortgage Encyclopedia. Copyright © 2004 by Jack Guttentag. Used with permission of The McGraw-Hill Companies, Inc.
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Regarding lender constraints, mortgage availability was measured by whether fixed rate mortgages were available to adjustable rate mortgage borrowers (FRMAV) and whether adjustable rate mortgages were available to fixed rate mortgage borrowers (ARMAV).
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* $12.5 million adjustable rate mortgage to refinance the loan for a mixed-use property on Henry Street in Philadelphia.
Wells Fargo admits that adjustable rate mortgages, which are loans that begin with low, seemingly manageable payments but eventually mushroom to exorbitant rates that few borrowers can afford, are unfair and harmful to borrowers.
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Guia para el consumidor sobre hipotecas a tasa ajustable (ARM) (Consumer Handbook on Adjustable Rate Mortgages) provides an overview of adjustable-rate mortgages (ARMs) and how they work.
In July the Federal Reserve Board released Spanish-language versions of two of its popular consumer brochures --Guia para el consumidor sobre hipotecas a tasa ajustable (ARM) (Consumer Handbook on Adjustable Rate Mortgages) and Lo que usted deberia saber sobre las lineas de credito con garantia hipotecaria (When Your Home Is on the Line: What You Should Know About Home Equity Lines of Credit).
Federal regulators from the FSLIC (Federal Savings & Loan Insurance Corporation) have discovered that consumers are overpaying on their adjustable rate mortgages by more than $8 billion as a result of interest rate miscalculations.
Throughout the seventies, as deposit interest rates rose, the thrifts had been pushing for adjustable rate mortgages, which would allow them to tie home loans to market interest rates.
Adjustable rate mortgages were higher as well, with the five-year ARM nosing up to 3.23 percent, and the 10-year ARM jumping to a 4-month high of 3.77 percent.
Five-year adjustable rate mortgages fell to 2.74 percent and one-year ARMs rose to 2.69 percent.

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