However, one of the top reasons for this, according to real estate news provider Realty Times, is that real estate agents know how to evaluate a property in terms of what is likely to garner the highest resale price. Therefore, they are likely to analyze the resale values of the properties they buy for themselves in an attempt to ensure a higher resale value.

Setting a price

According to the National Association of Realtors, people selling their homes often choose a price based on one of three factors: need, ego or greed. Particularly in a tough real estate market like the one we're seeing in the United States now, sellers often want to price their homes according to how much they need to get out of the sale in order to purchase a new property.

Unfortunately, what a seller needs to make on a property has nothing to do with market conditions, which are generally governed by supply and demand, along with other economic factors. The same goes for sale prices that are dictated by ego or greed. Just because a neighbor's house sold for an attractive price doesn't mean yours should as well, unless your home truly is more valuable or market conditions have changed.

Accepting an offer

The final piece of the puzzle in selling a house is deciding which offer to take. Levitt and Dubner say their data suggest that a real estate agent "holds out" for a higher price on his own home. Assuming this is true, it is important to remember that when it comes to selling his own home, the real estate agent is the decision-maker. When an agent is selling a client's home, that seller is in the driver's seat. The agent must balance his desire to get a price that will please the seller with the need to ensure that the home actually sells in a timely manner -- or at all.

When selling his own house, an agent can afford to gamble on the fact that a better offer might come along -- even though this plan will often fall through, particularly if the house stays on the market too long. This is much the same as when your stockbroker makes more money trading for herself than for you: She's willing to take more risks in her own account than she feels are appropriate in a client's account.

In addition, a common practice for real estate agents is to relist a home that isn't selling. This is because a listing's "days on market" can affect the price the seller can obtain for the property. When a home sits for too long, buyers assume the price is too high, the sellers must be desperate or there is something wrong with the property. This can kill a seller's chance of getting a fair price, and real estate agents must balance this risk with the seller's desire to hold out for a higher price.

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The bottom line

Type "real estate agents are" into a Google search bar and among the first options to appear are "scum," "crooks" and "liars." This may be why this little fact from "Freakonomics" has had so much staying power -- even though it was published more than five years ago. Perhaps real estate agents really do sell their own homes for more. But just as with many simple statistics, the data can tell us only that a correlation exists. The reasons why are left to speculation.

This article was reported by Tara Struyk for Investopedia.