Like stock performance, dividend yield is something that's best measured against a benchmark. As the yield for 10-year U.S. Treasury bonds has roughly doubled over the last two years to reach the neighborhood of 3%, that's changed the definition of "big yield" and shifted the priorities of investors seeking income-generating stocks. 

With that in mind, we asked three Motley Fool investors to identify some quality dividend stocks that currently offer a yield greater than 5%. Read on to see why they think Medical Properties Trust (NYSE:MPW), AT&T (NYSE:T), and TerraForm Power (NASDAQ:TERP) are top choices for investors on the hunt for big yield. 

Five stacks of coins increasing in size from left to right, with a block featuring a letter on top of each stack spelling out yield.

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Cashing in to continue growing

Matt DiLallo (Medical Properties Trust): Last year was a transformational one for hospital REIT Medical Properties Trust. The company invested $2.2 billion in expanding its real estate portfolio, which increased its asset base by 33%. Those new properties have helped boost cash flow, which has risen by a double-digit year-over-year rate over the past couple of quarters. That growing cash flow stream enabled the company to increase its dividend by 4.2% earlier this year, pushing its yield up to 7.2%.

Medical Properties Trust has been just as active in 2018. However, instead of buying properties, it has been cashing in on previous deals, which will give it the fuel to keep growing in future years. Last month, the company sold an investment it made in 2012, locking in a 13% return and providing it with $175 million in cash to reinvest in higher-returning opportunities. Meanwhile, earlier this month, Medical Properties Trust formed a joint venture that will own its 71 hospitals in Germany. That deal will enable the company to record a gain of several hundred million dollars while giving it more than $1 billion in cash to repay debt and reinvest in additional hospital properties.

While these transactions will slow its growth rate in the near term, cash flow growth should reaccelerate as the company finds the right deals to reinvest its windfall. Those future transactions will help strengthen the company's high-yielding dividend as well as increase the likelihood that Medical Properties Trust can continue growing its payout out in the coming years.

A top telecom dividend

Keith Noonan (AT&T): Based on the market's reaction, a significant portion of AT&T shareholders are not pleased with the recent completion of the company's acquisition of Time Warner. Shares have fallen roughly 7% since the deal was approved by the federal court that presided over the company's defense against the Department of Justice antitrust suit.

The sell-offs are likely tied to concerns about the $85.4 billion deal elevating the company's net debt to roughly $180 billion. That's no small sum, and the closing of the deal was followed by a cutting of AT&T's credit rating and some visible downgrades from analysts. However, the sell-offs have also pushed the company's already hefty yield up to 6.3% and its forward price-to-earnings ratio down to roughly nine.

True enough, the elevated debt levels might threaten the company's ability to maintain its dividend while still investing in the future of the business. That's far from a certainty, however.

Roughly half of the buyout was funded through stock. With AT&T's 34-year history of delivering annual payout growth, a reduction of its dividend could be expected to correspond with significant sell-offs, and that's something that AT&T and Time Warner were cognizant of prior to the merger. The telecom company's initial announcement of the deal also explicitly mentioned that the acquisition would improve its ability to cover its payout. That doesn't rule out the possibility of payout cut, but it does point away from one, and the cost of distributing its current dividend coming in at a reasonable 67% of trailing free cash flow bolsters that case. 

Overall, I think the deal will be beneficial and better position AT&T for success in today's highly competitive tech and telecom sector. The company now counts the Warner Bros. production studios, the Turner networks, HBO, and major entertainment franchises like the DC Comics universe and film rights to Game of Thrones and J.K. Rowling's Wizarding World under its corporate umbrella. That newfound content assets should help it tap into growth in the entertainment industry, add value to its telecom packages through bundling, and take advantage of synergies across businesses -- strengthening the long-term dividend picture.

A dividend powered by wind and sun

Travis Hoium (TerraForm Power): Renewable energy is one of the best places to find high-yielding stocks today and TerraForm Power is one of the industry's best. The company owns 2,606 MW of wind and solar projects, primarily in the U.S., and these projects have an average of 14 years of contracted energy sales remaining to utilities and other customers. This contracted cash flow is what makes the basis for its dividend. 

As of early May when the company reported earnings, it expected to pay a dividend of $0.76 per share this year, a yield of 6.5% based on today's stock price. To grow from there, management expects to keep 15% to 20% of the cash that's available for distribution to fund growth projects. 

What TerraForm Power has going for it that most yieldcos don't is a strong sponsor that wants to ensure the company's long-term viability. Brookfield Asset Management owns a controlling interest in the company and has proven it will backstop acquisitions to make sure they go through on favorable terms that will be accretive to the dividend. Having that kind of backing, along with over a decade of contracted cash flows, makes this a great dividend stock for investors.