Comments (scroll down to add your own):

1. An interesting point. Ran some numbers, and factoring in how much I overpay, my current interest rate, theoretical 15 year mortgage interest rate, it comes out that my monthly payment would increase by $30 more than what I overpay, minimum payment would increase by $90, be done 3 and a half years earlier, and save me $14000 in interest. I need to call my motrgage broker!

   Comment by Zachary Spencer — Feb 15th 2008 @ 11:22 am

2. This is a big difference between 15 and 30 year mortgages.

   For 30 Years: At a rate of 4%, you are looking at 14 YEARS to reach crossover. 8% is about 23 years.

   Even though a 15-year may cross over around 1-2 years, the general advice of it not making sense to prepay (or do a 15-year) makes sense.

   Comment by ntguru — Feb 15th 2008 @ 12:55 pm

3. Is there some software to help figure this stuff out? I could use some help.

   Comment by Ron@TheWisdomJournal — Feb 15th 2008 @ 10:48 pm

4. Ron,
   Try this…

   http://www.bankrate.com/brm/popcalc2.asp

   Comment by Dave — Feb 16th 2008 @ 7:39 am

5. …always remember you’re using a ‘Rubber-Ruler’ when calculating with ‘U.S. Dollars’ — especially with long term stuff like mortgages.

   “Inflation” constantly reduces the actual value (purchasing power) of a Dollar. That makes it much harder to calculate the ‘true’ mortgage crossover point.

   Of course, inflation is good news for mortgagees because you’re paying back the lender with paper Dollars worth less than those you borrowed to buy your house

   Over a 30 year mortgage period, say 1977 to 2007 — the Dollar lost over 70% of its value. $100,000 in 1977 is worth well less than $28,000 today, even by the official U.S. government statistics.

   Rubber-Rulers give you wrong answers.

   Comment by Caldwell — Feb 16th 2008 @ 1:19 pm

6. Caldwell: Valid point in general, but… In any given year a dollar of principal is equal to a dollar of interest. Now, if you were making an argument based on returns on money that you invest vs. prepaying your mortgage, then I’d buy your argument. But, in this case, no matter how much your money devalues between now and the crossover point, that point will still occur when the dollars toward principal = dollars toward interest.

   Comment by nickel — Feb 16th 2008 @ 1:44 pm

7. #
   Caldwell: Valid point in general, but… no matter how much your money devalues between now and the crossover point, that point will still occur when the dollars toward principal = dollars toward interest. {Comment by nickel}

   _____

   …so what’s the significance of a ‘crossover point’ anyway ??

   It’s significant because (without inflation) it marks the calendar date where the borrower starts seriously reducing the ‘principal’ (outstanding balance) of the money originally borrowed– and that’s the only way to ever pay off a loan.

   However, in our real American world, inflation has already seriously reduced that owed principal… long before that nominal crossover point.

   If one borrowed $100K on a 30-Year Mortgage in January 1977, the ‘principal’ owed to the lender would be $100K in January 1977 “U.S. Dollars”.

   However, in just 5 years (.. by Jan 1982) inflation reduced the actual value of that principal to only $63,000 (.. in 1982 Rubber-Dollars). The borrower did not have to wait 19.25 years on a paper to seriously reduce the principal he owed the lender — and it required no borrower effort or cost.

   And even at a nominal 19.25 year paper crossover point (..April 1996) — the real principal remaining was $38K. The mortgage borrower had already effortlessly reduced the principal he owed by over 60%… despite what the original 1977 amortization schedule said.

   ________

   That’s why inflation is such a disruptive force in our economy; few people understand it or can compensate for it overall. And inflation is always a deliberate Federal government policy (”legal counterfeiting” for government spending), not some mysterious force of nature or economics.

   The official CPI inflation rate is now about 4% annually. That rate is now over 7%, using the previous method of Federal calculation (before they ‘adjusted’ their methodology in the mid 1990’s to reduce “Official” inflation rates).
   Food & Fuel prices today average 13% higher than Jan 2007, even by official government statistics.

   What do think the U.S. Dollar wil be worth after 30 years, on a new mortgage today ?

   ========

   Comment by caldwell — Feb 17th 2008 @ 10:16 am

8. I continue to be torn between prepaying the mortgage and investing. I’m refinancing from a 6.375% 15yr to a 5.75% 30yr this week. My investment is buy-and-hold index funds, so I don’t have virtually any trading costs and the funds are low-turnover. I would love to be completely debt free, but I can’t help but think that this is more of an emotional decision than a logical one.

   Comment by CPA1298 — Feb 17th 2008 @ 8:39 pm

9. Caldwell: You’re arguing about something entirely different. My only point was to look at the fraction of your payment that goes toward principal vs. interest. Nothing more, nothing less. No matter how much you inflate (or deflate) the economy, it’s still a straight up, dollar-for-dollar comparison. When the amount of your payment going toward principal exceeds the amount going toward interest, you’ve reached what I (and another commenter) have termed the crossover point. I understand the effects of inflation perfectly well, and you’ve made a valid (and important) point about how the value of the money that you owe decreases over time. But it has nothing to do with the simple point that I was making.

   Comment by nickel — Feb 17th 2008 @ 8:48 pm

10. @ CPA 1298

    IMHO, a split is best.Take the extra you would be paying against your mortgage, split it in half, and invest half. If you don’t have alot of investments built up already, the mortgage can wait.

    If you’ve got a quarter mill in stocks already, then pay the mortgage off at any speed you so desire

    Zach

    Comment by Zachary Spencer — Feb 19th 2008 @ 10:17 am

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