# Paying Down Your Mortgage vs Investing More

Let’s do a little investment simulation. Don’t worry—I’ll do the math.

Jane has a \$5000 consumer loan and a \$20,000 stock portfolio. Her net worth is \$15,000. (Ah, the simple life of a person in a word problem.)

If the stock market goes up 10%, Jane makes \$2,000 and her net worth goes up to \$17,000 (\$22,000 in the portfolio, minus the \$5000 loan).

If the market goes down 10%, Jane loses \$2000. Are you with me so far?

Jane decides to pay off the loan. Her net worth is still \$15,000, but now it’s \$15,000 in stocks and no debt. Then the stock market goes down 10%, and Jane only loses \$1500. By paying off the loan (a financial nerd would call it “deleveraging”), Jane’s portfolio got less risky: The same change in the market caused a smaller change in her portfolio, even though her net worth stayed the same.

It doesn’t matter that Jane borrowed the money for a dining room set. As long as she owes the money, she’s taking on more investment risk than if she didn’t owe it. Her net worth fluctuates more with each day’s stock returns because of the debt. That’s not necessarily good or bad (maybe Jane wants to take on more risk in the hope of getting a bigger return) but it’s a mathematical fact.

This is all grade school math, right? But if we replace “consumer loan” with “mortgage,” somehow it makes otherwise intelligent people, investors and financial planners alike, forget basic arithmetic.

## “Investing on mortgage”

I’ll include myself among the mathematical amnesiacs, because I only came to understand this principle because of a recent blog post by Michael Kitces, director of research for Pinnacle Advisory Group, who writes the Nerd’s Eye View blog.

The post is written with financial planners in mind, not consumers, so I’m going to summarize it as follows: If you have both a mortgage and an investment portfolio, you’re probably making a big mistake. A big, fat, Greek default-style mistake.

Let’s go back to Jane. Now she has a \$100,000 mortgage, a \$100,000 house, and a \$200,000 stock portfolio. Her net worth is \$200,000 (the portfolio plus the house, minus the mortgage). When the stock market goes up 10%, Jane makes \$20,000. When it goes down 10%, she loses \$20,000.

Say Jane takes \$100,000 from her portfolio and pays off the house. Her net worth is still \$200,000, but her portfolio has dropped to \$100,000. Now when the stock market goes down 10%, Jane only loses \$10,000. Her portfolio got less risky, but her net worth stayed the same. (Yes, we’re assuming remarkable stability in the real estate market.)

Jane would tell you that she wasn’t borrowing money to invest in stocks, she was borrowing money to buy a house. Well, her portfolio and her bank don’t give a hoot. As long as she owes money, her investment performance has a bigger effect on her bottom line than if she didn’t owe.

After paying off her mortgage, Jane comes to you for financial advice. She’s thinking of taking out a new fixed-rate home equity loan to plump her portfolio back up to \$200,000. What is she, insane? If she’d decided not pay off her mortgage in the first place, she’d be in exactly the same position, with the blessing of most financial planners and, until recently, me.

Whether Jane knows it or not, she is borrowing against her house to invest in the stock market, and she should understand the risks.

## So what?

That sounded like a lot of academic drivel, I know. But if you’re a homeowner with a mortgage, it has real implications for your financial health. Assuming you’re in a position to save money beyond your mortgage payment, you are making a scaled down version of Jane’s decision every month: Pay down the mortgage, invest for retirement, or both?

“Each and every year I get to make a conscious decision about whether I want to implicitly buy stocks on mortgage by keeping the mortgage and buying stocks,” says Kitces. Or bonds, for that matter. Look at what you’re really doing:

Using borrowed money to buy bonds is stupid. Sure, mortgage rates are low. Bond rates are lower. Would you take out a 4% mortgage to buy bonds paying 2%? Me neither.

Using borrowed money to buy stocks is dangerous. Stocks are risky. Stocks bought with borrowed money are more risky. If you walk into a reputable financial planner’s office and tell them your financial plan is to borrow a bunch of money to invest in stocks, they will sit you down and give you a parental lecture about imprudent risk-taking. But if you’re using mortgage money to juice up your portfolio, somehow that’s okay?

Implicit in the idea that it’s okay to buy stocks “on mortgage,” as Kitces puts it, is the belief that stocks will definitely outperform in the long run. Jorie Johnson, a certified financial planner in Manasquan, New Jersey, doesn’t take a client’s mortgage into account when setting up their investment portfolio for this reason. “As long as you have a reasonable expectation of doing better in the market than your mortgage interest rate, you should be putting the money in the market,” she says.

However, this a point both technical and practical. If your goal is to shoot for the moon in your retirement portfolio by ratcheting up the risk with borrowed money, there’s a cheaper way to do the same thing by maintaining a smaller, but riskier, portfolio: Pay down the mortgage, but own more stocks and fewer bonds. You’ll lower your risk of ending up with negative home equity, save on mortgage interest, and achieve the same level of portfolio risk, with the same expected returns.

“Taking on more portfolio risk is the equivalent of having less portfolio risk but more leverage,” says Don St. Clair, a certified financial planner in Roseville, California. “If you’re not willing to take some of your portfolio and pay off your debt and jack the risk of your portfolio back up, then you shouldn’t be willing to keep the same portfolio and not pay off your debt.”

## The good old days

So, if you shouldn’t use borrowed money to buy stocks or bonds, what should you use it for?

Kitces just bought a house, and here’s his answer. “I’m really going to spend the bulk of the next ten years knocking this mortgage down to zero,” he says. “We are radically ratcheting down savings into investment accounts and really ratcheting up payments toward the mortgage.”

This feels intuitively wrong, doesn’t it? Everybody knows you should make retirement saving a habit and do it faithfully, month after month. Accelerating mortgage payments so you end up with a paid-off house and very little in other assets beyond an emergency fund and your 401(k) match can’t be a good idea, can it?

Just a couple of decades ago, it wasn’t just a good idea; it was conventional wisdom. “It was really straightforward: You built a giant down payment, you took on as little debt as possible, and whatever you did take on in debt, you knocked it out as quickly as possible,” says Kitces. “And when you actually got it done, you literally held a party and burned the mortgage note in your fireplace.”

Can anyone really say that isn’t still good advice? Oh, don’t explain it to me. Explain it to the Las Vegas homeowner who is \$100,000 underwater. Nobody needs to be told how toxic negative equity is in 2011, right? If anything, positive home equity offers more flexibility than a 401(k) balance. “They have home equity line of credit options, the ability to move, the ability to relocate, and the financial freedom to make decisions,” says Kitces.

## My money is trapped!

Now, wait a minute. Presumably, your investment portfolio is inside a 401(k) or IRA or some other box with “do not open until retirement” stamped on it. It would be crazy to pay the 10% penalty and a huge wad of taxes just to knock off a chunk of your mortgage.

I agree. So while you have a mortgage, what do you do with this money? You invest it in a way that reflects the fact that you’re playing with borrowed money. In other words, Johnny Mortgage’s portfolio should be invested heavily in bonds and cash. Remember that they’re not really bonds and cash. They’re stocks wearing disguises, because a portfolio of low-risk assets bought on leverage is still high-risk.

Even though it doesn’t often feel like it, a mortgage has an end. Later, when the mortgage is nothing but fireplace ashes, you can direct 100% of your former mortgage payment into your retirement savings.

## But mortgages are special

Mortgages are weird. Nowhere else in the world of finance can you get a 30-year fixed-rate loan with tax-deductible interest and the option to refinance if rates drop. Of all the kinds of debt, I’d probably agree that this is the best one to use to invest on leverage.

That still doesn’t make mortgage debt cute and cuddly. As the 23% of homeowners who are underwater know, mortgage debt can still bite you right where it hurts. Nearly all of those homeowners would have been better off paying down the mortgage rather than investing, or just keeping their investments in cash. (Yes, I know plenty of them did neither, which compounds the injury.)

Oh, there is one last wrinkle. In most states, you can walk away from a mortgage. The bank will take your house but can’t come after your other assets. As a forward-looking strategy, however, strategic default sucks. (Sorry for the parent lecture.) “Is your strategy for wealth creation really that you should buy real estate with as much debt as you can, because if it goes badly you can stick it to the bank?” says Kitces. “I don’t think that’s really how we’re telling people to build wealth.”

What do you think? Is there any defensible reason to buy stocks or bonds “on mortgage”? Or has everyone already forgotten 2008?

Matthew Amster-Burton is a personal finance columnist at Mint.com. Find him on Twitter @Mint_Mamster.