You may have heard that dividend stocks have significantly outperformed their stingier counterparts since 1972. You may have heard that the vast majority of the market's historical gains have come from dividends. And you may have heard that dividend payers are the best stocks to own during bear markets.

That's all true. In fact, during market downturns, dividend stocks outperform by as much as 1% to 1.5% per month.

But before you dive in and start buying dividend stocks, there's something you need to know.

Hold your horses
Dividend payers aren't all gumdrops and rainbows, as shareholders of dividend-slashers know all too well.

In 2009, S&P 500 companies skipped a record $52.6 billion in dividend payments. To avoid the next dividend implosion, you've got to keep an eye on a dividend payer's overall strength -- and its ability to pay those vaunted dividends. So as you're looking for dividend stocks for a bear market, keep an eye out for these red flags:

  • Extremely high yield
  • Industry headwinds
  • Spotty track record
  • High payout ratio

Extremely high yield
A yield that seems too good to be true usually is. An extraordinarily high yield is tempting, but such yields tend to show up when a stock has been beaten down -- which means investors don't have confidence in it.

Before Harley-Davidson (NYSE: HOG) reduced its quarterly dividend from $0.33 to $0.10 last year, the stock was "yielding" 10%. And when yields are high and investors still aren't buying? It's worth considering why other investors are wary of those tantalizing yields.

Industry headwinds
If an industry comes under attack -- as happens in cyclical industries and during economic crises -- there may not be any earnings to distribute, leading to dividend cuts or suspensions.

Investors looking to collect dividends over the next several decades from cyclical industries like energy may want to consider that, of all the S&P 500 members of the energy sector -- a group that includes such varied stalwarts as Chesapeake (NYSE: CHK), Noble (NYSE: NE), and Apache (NYSE: APA) -- only one, ExxonMobil, has managed to raise its dividend for 25 consecutive years.

Spotty track record
Companies with a checkered history of dividend payments aren't the strongest candidates for investment -- especially in a bear market, when external factors may strain their resources. Companies with a long and steady history of dividend increases, on the other hand, have demonstrated their reliability and are less likely to expose their investors to massive losses.

Procter & Gamble, a diversified consumer staples maker largely shielded from economic cycles, has paid an uninterrupted dividend since 1890. By contrast, mining giant Freeport-McMoRan Copper & Gold (NYSE: FCX) has only paid a steady dividend since 2003 -- and, as a result of industry headwinds, had to make a dramatic cut.

Of course, when history meets headwinds, sometimes the headwinds prevail. Despite nearly 100 years of maintaining or raising its dividend under its belt, General Electric (NYSE: GE) proved unable to shield itself from the industry headwinds this time around, and last year had to cut its dividend for the first time since 1938.

High payout ratio
A company's payout ratio -- usually calculated as dividends divided by net income -- is one of the most commonly used metrics to determine whether it can afford to continue paying its dividend at the same rate. A high payout ratio suggests that a company is returning the vast majority of its earnings to shareholders, and therefore may not have enough left over to fund future operations -- risking cut or suspended payments down the line.

Another good metric is dividends divided by free cash flow. Net income is an accounting construction that captures the gist of a company's operations, but it doesn't reflect how much cash a company actually has left over from its operations to cut your check.

Consider ruling out companies with a ratio greater than 80%, or those with negative free cash flow.

Two companies risking a blowup
So which companies will likely be the next dividend blowups? According to the above criteria, possibly these two:

Company

Yield

FCF Payout Ratio

Industry

GATX

3.8%

N/A

Distribution

CPFL Energia (NYSE: CPL)

6.4%

99%

Electric Utilities

Data from Yahoo! Finance and Capital IQ, a division of Standard & Poor's.

While their yields are only moderately high, their free cash flow payout suggests they may not be able to afford those payouts.

While GATX's rail fleet remains booked, lease rates are declining, and marine rates remain depressed. The company's CEO noted that "markets remain extremely challenging and competitive," and that pricing pressure will remain in force at least through 2010.

It's a similar story for CPFL, the Brazilian utility giant. Management has a stated policy of paying at least 50% of its net income in the form of dividends, but it tends to pay around twice that amount. Add in huge commitments to capital expenditures, and you have a company that has very little margin for error.

The silver lining ...
Dividend stocks have a history of putting money in investors' pockets, but choosing the right dividend stocks for a down market is critical to protecting your portfolio. Considering these warning signs of an unsustainable dividend will help you to achieve those golden returns that dividends have to offer.

If you'd like to see the dividend payers our team at Motley Fool Income Investor likes, including its six "buy first" stock ideas, you can try the service free for 30 days. Click here for all the details -- there's no obligation to subscribe.

Already a member of Income Investor? Log in at the top of this page.

This article was first published Aug. 25, 2008. It has been updated.

Ilan Moscovitz doesn't own shares of any company mentioned. Chesapeake is an Inside Value pick. The Fool has a disclosure policy.