Suspicious claims about borders, walls, ethanol and trade

CNN aired the 10th GOP presidential debate Thursday, a prime-time event starring the five remaining aspirants for the Republican nomination.

Not every candidate uttered statements that are easily fact-checked, but here are some suspicious or interesting claims.

"You look at our borders, they're like swiss cheese, everybody pours in."

- Donald Trump

Trump keeps saying undocumented immigrants are pouring over the U.S.-Mexico border, but that's not correct.

Data shows illegal immigration flows have fallen to their lowest level in at least two decades. The nation's undocumented immigrant population, which more than tripled to 12.2 million between 1990 and 2007, has dropped by about 1 million, according to the Pew Research Center.

The flood of undocumented immigrants from Mexico peaked in 2000, when more than 1.6 million people were apprehended, according to Department of Homeland Security data. Those numbers have decreased about 400,000 per year since 2012 and continued to go down in fiscal 2015.

An estimated 7 million undocumented Mexican immigrants were living in the United States at their peak in 2007, according to the Pew Hispanic Center's 2012 report. But there has been a sharp downward trend in net migration from Mexico since then, Pew found.

"The wall is $10 billion to $12 billion, if I do it."

- Trump

Trump used to say that a 1,000-mile-long wall with Mexico would cost $8 billion, but now he says it would cost $10 billion to $12 billion. But that's also a dubious estimate, according to experts in the construction industry, based on Trump's previous comments that the wall would be made of precast concrete slabs, rising 35 to 40 feet.

Israel has spent $2.6 billion on a 325-mile-long barrier bordering the Palestinian territories. But only one-tenth (33 miles) of the Israeli barrier is a 25-foot-high concrete wall. The rest is a six-foot-high electronic fence.

A retired construction estimator said a wall, as described by Trump, would cost at least $25 billion - and that is not counting a video system to keep watch on the border. Building the wall would also require at least 40,000 workers a year for at least four years, but he doubted it could be built so quickly.

The concrete panels would need to be at least eight inches thick and 40 feet tall (35 feet above ground and five feet under ground). He estimated that it would cost about $10 billion for the concrete panels and $5 billion to $6 billion for steel columns to hold the panels, including labor. Concrete footing for the columns and a concrete foundation would add another $1 billion. A road would need to be built so 20-ton trucks could deliver the materials; that's another $2 billion. Then you need to add another 30 percent for engineering, design, management and so forth.

The foundations would require nearly 2.5 million to 3 million cubic yards of concrete, which requires poured-in-place concrete delivered in trucks. That's 250,000 to 300,000 truckloads, 20 tons of concrete each. Then the excavated earth would need to be hauled somewhere and disposed of - nearly 3 million cubic yards, or enough soil to cover 17 acres 100 feet deep. That's 90,000 truckloads of 40 tons each.

The ethanol mandate is "phasing out now. By 2022, that program expires, by virtue of the existing law. It will go away."

- Marco Rubio

Rubio, like many politicians, gets the phaseout of the ethanol mandate wrong.

The federal renewable-fuel mandate sets the minimum amount of corn-based ethanol to be mixed into gasoline to reduce or replace fossil fuels. Congress created the Renewable Fuel Standard in 2005 and set the minimum required volume of renewable fuel to be mixed into the U.S. gasoline supply each year.

Currently, the law lists the minimum volume of renewable fuel through 2022. That's what most people refer to when they say the mandate will "expire" or "phase out" after 2022.

But that's not correct. The mandate doesn't go away at all. The program is set to go on indefinitely unless repealed by legislation. In fact, statutes require that after 2022, the Environmental Protection Agency set the minimum levels through regulations.

"I don't mind trade wars when we're losing $58 billion a year [to Mexico], you want to know the truth. We're losing so much. We're losing so much with Mexico and China - with China, we're losing $500 billion a year."

- Trump

Trump has the numbers right on the trade deficit with Mexico and overstates it with China - but he gets the economics very wrong in both cases. A trade deficit means that people in one country are buying more goods from another country than people in the second country are buying from the first country.

So in Mexico's case, Americans purchased $294 billion in goods from Mexico, while Mexico purchased $236 billion in goods from the United States. That results in a trade deficit of $58 billion in 2015. In the case of China, Americans bought $482 billion in goods from China, while Chinese purchased $116 billion from the United States, for a trade deficit of $366 billion.

But that money is not "lost." Americans wanted to buy those products. If Trump sparked a trade war and tariffs were increased on those Chinese goods, then it would raise the cost of those goods to Americans. Perhaps that would reduce the purchases of those goods and thus reduce the trade deficit - but that would not mean the United States would "gain" money that had been lost.

Trump frequently suggests, as he did in the debate, that Mexico could pay for the wall out of the $58 billion trade deficit. But that is nonsensical. The trade deficit does not go to the government; it just indicates that Americans are buying more goods from Mexico than the other way around.

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An award-winning journalism career spanning nearly three decades, Glenn Kessler has covered foreign policy, economic policy, the White House, Congress, politics, airline safety and Wall Street. He was The Washington Post's chief State Department reporter for nine years, traveling around the world with three different Secretaries of State. Before that, he covered tax and budget policy for The Washington Post and also served as the newspaper's national business editor. Kessler has long specialized in digging beyond the conventional wisdom, such as when he earned a "laurel" from the Columbia Journalism Review