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Comparison formula helps determine right mortgage for you

As indicated last week, the annual percentage rate, or APR, the law requires mortgage lenders to disclose alongside the interest rate is not a useful measure of cost to the borrower. Expressed as a percent, it makes no intuitive sense to most borrowers, does not yet cover all costs, and does not take account of differences in borrower time horizons, tax rates and opportunity costs.

A much more useful measure is the "time horizon cost," or THC, that is described below.

The THC is the total cost of the mortgage in dollars over the period the borrower expects to be in the house. I will illustrate it with the example I used last week of a borrower choosing between a fixed-rate mortgage at 5.125 percent and zero points, and another at 4.25 percent and 4.4 points. The loan amount is $100,000 and settlement costs other than points are $1,000 in both cases.

I am going to assume initially that the borrower expects to be in the house four years, is in the 15 percent tax bracket, and has an opportunity cost - the return he can earn on other investments - of 2 percent. The THC for the borrower on the 4.25 percent mortgage consists of the following:

Total monthly payments of principal and interest over four years: $23,613

Lost interest on monthly payments: $803

Points paid upfront: $4,400

Other settlement costs paid upfront: $1,000

Lost interest on points and other settlement costs: $380

Total costs: $30,196

From these costs, we subtract cost offsets:

The borrower's tax savings on interest: $2,548

The borrower's tax savings on points: $700

Reduction in loan balance: $7,195

Total offsets: $10,442

Total cost net of offsets: $19,754

When we do the same for the 5.125 percent mortgage, the total net cost is $18,768, or $986 less. (Note: The detail is omitted to save space, complete data will be available on my Web site.) The high-rate mortgage with zero points is the better deal.

But the results are sensitive to the specific features of the borrower. If we change the borrower's time horizon from four years to eight years, the results are reversed, with the low-rate mortgage becoming the better deal because the lower rate extends over a longer period. If we then raise the borrower's opportunity cost from 2 percent to 12 percent, keeping everything else the same, the advantage flips back to the 5.125 percent mortgage because of the larger interest loss on the points paid upfront. If finally we raise the borrower's tax rate to 40 percent, the advantage flips back once more to the 4.25 percent mortgage because of the larger tax savings on the points.

In using the THC, there is no need for borrowers to become enmeshed in the details. So long as they have confidence in the source, many - perhaps most - borrowers will be satisfied with the single bottom line number. Borrowers seeking understanding, however, have access to the detail that will help them understand why the results are what they are. This educational process is not possible with the APR.

All the numbers referred to above were drawn from calculator 12ci on my Web site, which was programmed to compare the THCs of different FRMs. Other calculators compare different adjustable-mortgages, and ARMs versus fixed rates. Stand-alone calculators like mine, however, require the borrower to enter the relevant prices. This is not nearly as useful to borrowers as receiving THCs based on the prices actually being quoted to them by loan providers.

One way that could happen would be that the Truth in Lending Act is revised to replace APR with THC. The likelihood of that happening within my lifetime is vanishingly small. The other way is that a private firm, looking to acquire a competitive advantage, builds THC into its loan origination platform as a way of creating additional value for borrowers. I am quite confident that will happen during my lifetime.

• Contact Jack Guttentag via his Web site at mtgprofessor.com.

Inman News Service

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