Once again, we present a list of our most popular fact checks of the past year.

It’s a top 10 list, but we actually have 11 entries because two fact checks about newly elected Rep. Alexandria Ocasio-Cortez (D-N.Y.) ended up in a tie for 10th place.

Six of the most-read fact checks were about President Trump, which should not be a surprise given how he dominates the news. In compiling the top 10 list, we focused on full fact checks of specific claims. Thus we did not include roundups of speeches or announcements on this list, but if we had, our dissection of the president’s op-ed for USA Today on Medicare would have made the cut. Our announcement of a new category, the Bottomless Pinocchio, also would have appeared in the top 10 list.

In terms of reader interest, it was yet again a banner year for the Fact Checker, especially for our videos, which have attracted a vast and growing audience. Thus we also listed five of our most popular videos, as well as the top fact checks that were published in several years before 2018.

(Meanwhile, we’re going to try to take a needed break before the new year. We will publish an update of our database of Trump’s false and misleading claims before year’s end, but other than that, we do not plan any fact checks. Only something really dramatic will cause us to change our plans.)

Click on the headline if you want to read the full column.

1. The facts about Trump’s policy of separating families at the border

Trump and administration officials said U.S. laws or court rulings forced them to separate families caught trying to illegally cross the southern border. Officials would have you believe their hands are tied. Except they aren’t.

In April 2018, then-Attorney General Jeff Sessions rolled out a zero-tolerance policy that orders Department of Homeland Security officials to refer any adult “believed to have committed any crime, including illegal entry,” for prosecution. Illegal entry is a misdemeanor for first-time offenders, and conviction is grounds for deportation. The government, however, is also required to place children with family members whenever possible, and if that isn’t possible, attempt to place them in foster care.

In other words, children go through a process and are eventually placed with sponsors in the country, while their parents are prosecuted and potentially deported. This is all because the Trump administration, under its zero-tolerance policy, is choosing to prosecute border-crossing adults for any offense, something previous administrations have declined to do. (This fact check earned the biggest readership in The Fact Checker’s 11-year history.)

Four Pinocchios

Administration officials have pointed to "the law" as the reason why undocumented children are being separated from their parents. But there's no such law. (Meg Kelly/The Washington Post)

2. Just about everything you have read about Sen. Warren’s DNA test is wrong

After being egged on by Trump, Sen. Elizabeth Warren (D-Mass.) released the results of a DNA test Oct. 15 that indicated she had a Native American ancestor. The results — which identified Native American DNA from six to 10 generations ago — were immediately misinterpreted. Soon it was reported that Warren had less Native American DNA than the average European American.

But it turns out reporters and politicians are not very good at understanding genetics. So we set the record straight, after reviewing the results in detail and consulting with genetics experts.

As one might expect, the vast majority of Warren’s DNA — 95 percent — indicated European ancestors. But five genetic segments were identified, with 99 percent confidence, as being associated with Native American ancestry. Ancestors do not contribute genetic material equally over time. Contrary to the initial reporting, the percentage of Native American DNA in her genome does not shrink as you go back generations. There could be one individual in the sixth generation — living around the mid-1800s, which is similar to Warren family lore — or possibly a dozen or more ancestors back to the 10th generation, which would be about 250 years ago. Her results are consistent with a single ancestor, however.

Bottom line: Warren’s Native American DNA, as identified in the test, may not be large, but it’s wrong to say it’s as little as 1/1,024th or that it’s less than the average European American.

Reporters and politicians rushed to say her DNA test shows she was only 1/1024th Native American. But that's a huge misinterpretation of the data. (Meg Kelly/The Washington Post)

3. Once again, ‘fake news’ decried by Trump turns out to be true

There have been several instances in which the president or his surrogates have flatly denied something — only to have that denial contradicted weeks or months later by new documents or statements. Often, by then the media coverage has moved on to a new controversy.

So The Fact Checker looked at four times when either the administration admitted or official records showed the initial denial was false: Trump knew nothing about Stormy Daniels, Karen McDougal or payoffs; the president had no role in Donald Trump Jr.’s statement on the Russia meeting; Michael Flynn did not discuss sanctions with the Russians; the president did not give classified information to Russia.

The Trump administration has a consistent habit of flatly denying media reports that turn out to be correct. (Meg Kelly/The Washington Post)

4. Fact-checking Bill Clinton’s meltdown on NBC’s ‘Today' show

The former president, challenged about how his sexual transgressions look in the #MeToo world, responded with a defense that stressed how much he had done for women as a politician. He bragged women were overrepresented in his office “for their percentage of the bar” when he was attorney general. That’s a weak argument considering between 1918 and 1970, only 164 women gained Arkansas law licenses. He touted the fact that he “had a sexual harassment policy when [he] was governor in the ’80s.” Except, Clinton wasn’t setting an example with the policy; his office was merely implemented new federal guidelines.

Then, while saying “nobody believes I got out of [the Lewinsky scandal] for free,” he noted that he left the White House “$16 million in debt.” He didn’t. He did have large legal debts, perhaps several million as he once said, but $16 million is a clear exaggeration. Regardless, the Clintons were able to dig themselves out of that hole fairly quickly.

Three Pinocchios

The former president made a number of claims on NBC's "Today Show" that do not pass scrutiny. (Meg Kelly/The Washington Post)

5. Fact-checking Trump’s error-filled tweetstorm on the Russia investigation

In a February tweetstorm that started late on a Saturday and continued into Sunday morning, the president railed against the investigation into Russian interference in the 2016 election.

We offered a guide to Trump’s many misstatements and misleading claims in this Twitter barrage, including that he “never said Russia did not meddle,” that the FBI is “spending too much time trying to prove Russian collusion” and that “Collusion was between Russia and Crooked H, the DNC and the Dems.”

6. Not just misleading. Not just false. A lie.

The first denial that Trump knew about hush-money payments to silence women came four days before he was elected president, when campaign press secretary Hope Hicks said, without hedging, “We have no knowledge of any of this.”

The second came in January of this year, when then-Trump attorney Michael Cohen said the allegations were “outlandish.” By March, two of the president’s spokespersons — Raj Shah and Sarah Sanders — said publicly that Trump denied all the allegations and any payments. Even Cohen’s attorney, David Schwartz, got in on the action, saying the president “was not aware of any of it.”

In April, Trump finally weighed in, answering a question about whether he knew about a payment to porn star Stephanie Clifford, who uses the stage name Stormy Daniels, with a flat “no.”

The Fact Checker reviewed the indisputable evidence that Trump and his allies had been deliberately dishonest at every turn in their statements regarding payments to Daniels and Playboy model Karen McDougal. For the first time, we labeled a politician’s statement a lie.

The Post's Fact Checker Glenn Kessler explains why he's labeling President Trump's claims about Michael Cohen and Stormy Daniels "a lie." (Monica Akhtar/The Washington Post)

7. What’s the immigration status of Melania Trump’s parents?

As the congressional debate over immigration ramped up, Trump regularly railed against “chain migration,” including the granting of immigration visas to parents of U.S. citizens. This left several readers wondering how, exactly, the president’s in-laws were in the country. First lady Melania Trump is, after all, an immigrant, and if she sponsored their visas, Trump’s rhetoric would be hypocritical.

According to various news reports, the first lady’s parents had been living in the United States for at least a year and probably longer — possibly since the mid-2000s. Immigration experts said there were four possible explanations: They had legal permanent residence, an extended tourist visa, parole or a student visa. The most logical possibility (and, it turns out, the correct one) is also the most problematic considering the president’s policy position — they were legal permanent residents. Their attorney declined to tell The Washington Post how or when they gained their green cards.

In August, they became U.S. citizens.

President Trump has railed against "chain migration." His wife is an immigrant and his in-laws are in the U.S., but how did they come in? (Meg Kelly/The Washington Post)

8. President Trump announces a major U.S. Steel expansion that isn’t happening

Trump announced the chief executive of U.S. Steel told him the company was opening six new major facilities. Because it is a publicly traded company, it is supposed to disclose any materially important information. This would have been huge news.

The president has a habit of citing conversations that didn’t occur quite the way he describes them. One would think this would be fairly easy to clear up but neither the White House nor the chief executive of U.S. Steel responded to inquiries. A spokeswoman for the company noted that all major announcements were posted online. There was no announcement of six new facilities.

Translation: The president is wrong, but U.S. Steel was afraid to say that out loud, even after Trump kept making the claim and inflating it to eight or nine new facilities. Eventually, Trump said it enough times that it ended up on our list of Bottomless Pinocchios.

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9. Beto O’Rourke’s false claim that he did not leave scene of DWI

During a debate with his rival, Sen. Ted Cruz (R-Tex.), Rep. Beto O’Rourke (D-Tex.) was asked point-blank about a drunken-driving incident when he was 26: Did he try to leave the scene of the crash?

Texas newspapers had obtained police reports of the collision and reported that O’Rourke had done so. O’Rourke flatly denied trying to leave the scene of the crash, but that is contradicted by a witness statement in the police reports, which also said O’Rourke was so drunk that he could barely get out of the car without falling. Given his blood alcohol content at the time of the crash, O’Rourke’s memory 20 years after the fact is not nearly as credible as the police reports written just hours after the crash. (In a statement after the fact check appeared, O’Rourke claimed he had reached out to the passenger in his car — whom he did not identify — and she said he did not try to flee.)

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10. Fact-checking Alexandria Ocasio-Cortez’s media blitz

Alexandria Ocasio-Cortez, the 29-year-old self-described “democratic socialist” who won a seat in Congress, came under fire dismissing concerns about the anticipated costs of her proposals and offering too-glib answers. This fact check offered a dissection of some of her eyebrow-raising claims, including: “Unemployment is low because everyone has two jobs. ICE is required to fill 34,000 beds with detainees every single night. The upper-middle class does not exist anymore in America. The reason that the Supreme Court upheld the Affordable Care Act is because they ruled that each of these monthly payments that everyday American make is a tax.”

The self-described “democratic socialist” keeps making statements that are false, misleading or incorrect. (Meg Kelly/The Washington Post)

10. Alexandria Ocasio-Cortez’s $21 trillion mistake

Ocasio-Cortez, in a December tweet, said that expanding Medicare to people under 65, known as Medicare-for-all, could be paid for in part with $21 trillion in “Pentagon accounting errors.” As she put it, “66% of Medicare-for-all could have been funded already by the Pentagon.”

But the $21 trillion is not one big pot of dormant money collecting dust somewhere. It’s the sum of all transactions — both inflows and outflows — for which the Defense Department did not have adequate documentation.

We put $21 trillion in context. The entire national debt is $21.8 trillion. According to the Congressional Budget Office, total defense spending from 1998 to 2015 was nearly $9 trillion. The CBO estimates $7 trillion in defense spending from 2019 to 2028. In other words, completely defunding the military for the next decade would yield only one-fifth of $32 trillion, the common estimate of the 10-year cost for single-payer health care. That’s a much better way of illustrating the cost of Medicare-for-all.

Four Pinocchios

Top videos

A fact: More people watch our videos than read our fact checks. Videos have given us a different option to tell particularly visual and complicated stories in new ways. Videos updating readers on our database of Trump’s false or misleading claims remain wildly popular. Many of the videos above were hugely popular. The ones listed below also ranked among the top performers.

Top five columns in 2018 — that were published before 2018

Many readers discover old fact checks when searching the Internet for information. Here’s a list of fact checks that ranked among the top 75 in 2018 — even though they were first published in 2017, 2016 or even 2015.

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