Fact-checking Democratic candidates on the issues at the ABC News debate in Houston

Here's ABC News' fact check of the Democratic Debate in Houston between Sen. Amy Klobuchar, Sen. Cory Booker, Mayor Pete Buttigieg, Sen. Bernie Sanders, former Vice President Joe Biden, Sen. Elizabeth Warren, Sen. Kamala Harris, Andrew Yang, former Rep. Beto O'Rourke and former Housing and Urban Development Secretary Julian Castro.

Booker comparing today's gun violence to past wars

Booker: "We have had more people die due to gun violence in my lifetime than every single war in this country combined from the Revolutionary War until now."

The Facts: Booker's assertion appears to be right, based on available information about fire-arm related deaths. Booker was born on April 27, 1969. While data specific to that date is not publicly available, data for the number of fire-arm related deaths collected by the Centers for Disease Control and Prevention shows that since 1968, 1,559,048 have died from fire-arm related injuries. That said, "fire-arm related" injuries includes death by suicide and other non-violent gun accidents.

When it comes to people killed in U.S. military conflicts, it gets a little more tricky. The Congressional Research Center's most recent data shows that 1,003,982 people have died. CRC's reported data from the Civil War, however, counts only Union soldiers, not those who fought for the Confederacy died in the Civil War, nor does it consider deaths in Afghanistan, Iraq or Syria. Adding the Department of Defense's estimated 6,700 deaths in the recent Iraq, Syria and Afghanistan conflicts, along with expert's latest numbers for the Civil War --including the Confederate soldiers -- the total number of deaths related to U.S. conflicts comes to roughly 1,396,000. That number is lower than the number of people who have died from fire-arm related injuries since Booker's birth.

--Allison Pecorin

Klobuchar estimates 149 million would lose their insurance on Medicare-for-all plan

Klobuchar: "While Bernie wrote the bill, I read the bill. And on page eight -- on page eight of the bill, it says that we will no longer have private insurance as we know it. And that means that 149 million Americans will no longer be able to have their current insurance. That's in four years. I don't think that's a bold idea, I think it's a bad idea."

The facts: Klobuchar's estimate might have actually been low. According to a 2017 Congressional Research Service report, 67.5% of the U.S. population in 2016 had private health insurance coverage "during all or part of the year." That's about 216.2 million people who had private coverage "through either the group or the non-group market," the report said. That means as many as 67 million more people could lose their current insurance than Klobuchar estimated.

--Sophie Tatum and Lauren Lantry

Booker on African Americans and criminal justice

Booker: "We have more African Americans under criminal supervision today than all the slaves in 1850."

The facts: Booker appears to be referring to the 2011 book, "The New Jim Crow: Incarceration in the Age of Colorblindness." The author, Ohio State law professor Michelle Alexander, said there were more African American men in the prison system today -- in prison, jail, probation and parole -- than who were enslaved in 1850.

According to the Census Bureau, there were about 3.2 million slaves in 1850. That included 872,924 men.

In 2017, the Justice Department estimated there were 726,000 African Americans in jail or prisoners and another 1,302,252 were under parole or probation.

That means 2,028,252 African Americans were under supervision of the criminal justice system in 2017, which is fewer than total slaves in 1850.

-- Zachary Kiesch

Harris takes credit for Los Angeles' blue skies

Harris: "I took on the big oil companies, and we saw progress. If any of you have been to Los Angeles 20 years ago, you'll remember, that sky was brown. You go there now, the sky is blue, and you know why? Because leaders decided to lead, and we took on these big fossil fuel economies."

The facts: Air quality in the Los Angeles has improved significantly since the late 1970s, according to the South Coast Air Quality Management Board and the area appeared to make gains during Harris' time working as the state's top prosecutor. But experts have raised concerns that progress has stalled in recent years.

The Health of the Air Report compiled by researchers at New York University and the American Thoracic Society, ranks Los Angeles the number one city for increases in deaths linked to air pollution since 2010.

Parts of Los Angeles county do not meet requirements to reduce ozone pollution under the Clean Air Act, according to the Environmental Protection Agency, which will require officials to submit a plan to federal officials laying out a plan to address the problem. Ground-level ozone that contributes to bad air quality days is released from vehicles, power plants, and industrial facilities and is worse in warmer temperatures.

--Stephanie Ebbs

Castro on Trump's trade war costing US families $600

Castro: "It's estimated that (the U.S.-China trade war) cost $600 to the average American family."

The facts: It's true that costs from the U.S.-China trade war will be passed on to American consumers.

Economists generally believe that tariffs on imported goods are indeed taxes that either businesses or consumers end up paying. While some economists argue that importers will receive a discount on Chinese goods because its currency has devalued during the trade war, most economists also say the costs associated with tariffs are eventually passed on to consumers. Businesses do this by raising the cost of the impacted good, which means consumers pay more in the end.

Castro is citing a study from non-partisan Congressional Budget Office which finds that tariffs on Chinese imports will reduce average American household income by approximately $600 by the year 2020.

--Matthew Vann

Klobuchar disputes account of record as Minnesota prosecutor

The facts: ABC News Correspondent Linsey Davis pressed Klobuchar on her record as a prosecutor in Minnesota, noting that she did not prosecute a single case of the "dozens of incidents" in which citizens were killed by police.

Klobuchar answered that it was "not my record." However, she didn't directly dispute the statement itself. She instead noted that her office had opted to task the cases with "outside investigators" and put them before a grand jury to consider charges.

But according to a report from American Public Media and Minnesota Public Radio earlier this year, that approach was criticized by some of the victim' families, as grand jury procedures are kept secret. A 2017 paper in the Harvard Law Review broadly described the perception of grand juries increasingly as being "used in furtherance of governmental goals -- while acting as the prosecutor's shield from the prying eyes of the public."

Klobuchar appeared to acknowledge that as an issue, adding in the debate, "I now believe it is better for accountability if the prosecutor handles them and makes those decisions herself."

-Alexander Mallin

Biden on Afghanistan being three countries

Biden: "The whole purpose of going to Afghanistan was to not have a counterinsurgency, meaning that we're going to put that country together. It cannot be put together. Let me say it again. It will not be put together. It's three different countries."

The facts: Biden was asked a question that included a reference to Afghanistan though the thrust of the question was whether it was wrong for the Obama administration to pull out of Iraq because it led the Islamic State to fill in the power vacuum. It's possible that Biden was jumping from Afghanistan to Iraq.

At the height of the Iraq War in 2006, Biden said Iraq should be decentralized into semi-autonomous states under a federal government divided along the three large ethnic communities in that country -- Sunni Muslims, Shiite Muslims and the Kurds. Laid out in a New York Times op-ed then-Sen. Biden and his co-author Leslie Gelb suggested the idea as an option for winding down the U.S. troop presence in Iraq without leaving behind an unstable security situation.

Afghanistan is a multi-ethnic country with a Pashtun majority located mainly in the eastern and southern parts of the country and Tajiks and Uzbek minorities are located in northern Afghanistan. While the conflict in Afghanistan has been divided somewhat along ethnic lines, it has not been suggested that Afghanistan is made up of three different countries.

--Luis Martinez

Castro on Biden's memory

Castro to Biden: "Are you forgetting already what you said just two minutes ago? I can't believe that you said two minutes ago that they had to buy in, and you're saying they don't have to buy in. You're forgetting that?"

The facts: Biden used the term "buy in" with regards to his health care plan. But his statement requires more context.

"Look, everybody says we want an option. The option I'm proposing is, Medicare for all -- Medicare for choice. If you want Medicare, if you lose the job from your insurance company, from your employer, you automatically can buy into this," Biden said.

Under Biden's health care plan, people who want to keep their health insurance they receive through their job can keep it. But anyone who doesn't like their insurance has the ability to "buy in" to a Medicare-like public option.

Biden's plan would also allow for any individual who would qualify for Medicaid under the Affordable Care Act expansion to get access to his public option without premiums, but it is unclear if this would be an automatic enrollment, or an opt-in.

These details weren't immediately clear, however, when the former vice president said people could automatically "buy in."

At a later point in the debate, he said people would be automatically enrolled in Medicare if they could not afford health insurance. He said, "Anyone who can't afford it gets automatically enrolled in the Medicare-type option we have."

It's unclear to what Biden is referring when he says "buy in," because when challenged by Castro, Biden said repeatedly, "They do not have to buy in. They do not have to buy in."

--Trish Turner and Molly Nagle

O'Rourke says wall produced 'thousands' of deaths

O'Rourke: "Democrats and Republicans alike voted to build a wall that has produced thousands of deaths of people trying to cross to join family or to work a job."

The facts: Critics, including O'Rourke, have long maintained that creating imposing barriers at the border will only force people to see other more dangerous ways to cross.

According to U.S. Customs and Border Protection, the U.S. Border Patrol has recorded since 1997 between 263 and 492 deaths along the southern border each year. Immigrant aid workers estimate that number could be even higher. The majority of recorded deaths were recorded in remote areas and places where border barrier construction is limited by the Rio Grande River. It's unclear, if those who died were attempting to maneuver around the current barriers.

And a 2010 report from the Congressional Research Service found "considerable evidence" that ramping up security in urban border areas led migrants to cross in more remote and dangerous places.

In blaming both Democrats and Republicans, O'Rourke is likely referring to the budget stalemate earlier this year that resulted in the longest government shutdown in American history. Democrats ultimately agreed to $1.4 billion dollars for 55 miles of large steel fencing, designs used under previous administrations. It was significantly less than the $5.7 billion Trump had wanted.

--Quinn Owen

Klobuchar on Trump tariffs costing 300,000 US jobs

Klobuchar: "If we're not careful, he's going to bankrupt this country. One forecast said it's already said it cost us 300,000 jobs, all right?"

The facts: It's true that Trump's trade war has indeed cost American jobs. When the president announced a 10% tariff on $300 billion in Chinese goods, China struck back and announced it would stop buying any American agricultural products -- negatively affecting many U.S. farm businesses.

China's retaliatory moves have also brought U.S. farm sales of soybeans to record lows, as China is the world's largest purchaser of soybeans.

Klobuchar appears to be citing a Moody's Analytics report which finds the trade war has cost 300,000 U.S. jobs.

--Matthew Vann and Philip Wang

Biden and Sanders spar on cost of health care

Biden: "My plan for health care costs a lot of money. It costs $740 billion. It doesn't cost $30 trillion -- $3.4 trillion a year, it turns out, is twice what the entire federal budget is … "

Sanders: "That's right, Joe. Status quo over 10 years will be $50 trillion."

The facts: At issue is how much a government-run health care plan would cost, and that would depend greatly on how that plan is set up. Overall though, Biden and Sanders actually agree that $30 trillion is a good estimate of what Sanders wants.

It's likely they are looking at a 2016 report by the nonprofit Urban Institute found that if Sanders' plan were enacted, between the years 2017 and 2026, "federal expenditures would increase by $32.0 trillion over that period."

As for the $50 trillion estimate cited by Sanders, National Health Expenditure Projections by the federal government's Centers for Medicare and Medicaid Services found that "under current law, national health spending is projected to grow at an average rate of 5.5 percent per year for 2018-27 and to reach nearly $6.0 trillion by 2027."

--Sophie Tatum

Biden on immigration detention

Biden: "We didn't lock people up in cages. We didn't separate families. We didn't do all of those things."

The facts: The Obama administration detained undocumented immigrants, including families, at border facilities that often included chain-link fencing that critics have called "cages." Border authorities have argued that these holding facilities are temporary, until people can be processed and either released or sent to another more permanent shelter. In 2015, the American Immigration Lawyers Association filed a formal complaint against a family detention center run by U.S. Immigration and Customs Enforcement, citing a lack of access to medical care for detainees.

On family separations, the Obama administration -- like the Bush administration – did separate parents from children but only in rare circumstances when the child's safety might be at risk or a crime committed.

In contrast, the Trump administration enacted a "zero-tolerance" approach in April 2018 that called for stepped-up prosecutions of any adult crossing the border illegally, even without evidence of a serious crime. The result was some 2,700 children were separated from their families in a matter of weeks.

Both President Barack Obama and Trump asked a federal judge for permission to detain families together long term, but were rejected both times.

--Quinn Owen

O'Rourke and Castro tie Trump rhetoric to shooting

O'Rourke: "A racism and violence that had long been a part of America was welcomed out into the open and directed to my hometown of El Paso, Texas, where 22 people were killed, dozens more grievously injured by a man carrying a weapon he should never have been able to buy in the first place, inspired to kill by our president."

Castro: "A few weeks ago, a shooter drove 10 miles inspired by this -- 10 hours inspired by this president to kill people who look like me."

The facts: According to a police affidavit, the 21-year-old man accused opening fires at a Walmart in El Paso, Texas, which left 22 dead and dozens more injured, said he was targeting "Mexicans."

The El Paso police chief said authorities were also examining what he called a "manifesto" that they believed was written by the shooter and published online less than an hour before the shooting occurred. The document decried what the author believed was an ongoing "invasion" of Texas by Hispanic people and what the author foresaw as the impending destruction of America.

The document posted online anticipated the attack would be connected to President Donald Trump's rhetoric, and the author said that his ideology predated Trump and hadn't changed for years.

Trump has repeatedly warned of an "invasion" of immigrants multiple times, including in a tweet on Jan. 31: "More troops being sent to the Southern Border to stop the attempted Invasion of Illegals, through large Caravans, into our Country. We have stopped the previous Caravans, and we will stop these also. With a Wall it would be soooo much easier and less expensive. Being Built!"

His campaign also has ran many online ads that used the word "invasion."

--Quinn Scanlan

Castro on Biden's health care plan

Castro: "Of course, I also worked for President Obama, Vice President Biden, and I know that the problem with your plan is that it leaves 10 million people uncovered. Now, on the last debate stage in Detroit, you said that wasn't true and Sen. Harris brought that up. There was a fact check of that. They said that was true."

The facts: This 10 million number has come up in past debates as a dig against Biden's plan. Biden's health care plan, according to his campaign website, would insure "more than an estimated 97% of Americans." There would be roughly 3% of people who would not be covered under this plan. That 3% comes out to be about 9.8 million people.

--Sophie Tatum

Harris on Trump's DOJ and the ACA

Sen. Kamala Harris: "Donald Trump's Department of Justice is trying to get rid of the Affordable Care Act."

The facts: Harris is referring to the Justice Department's move this past March in a major lawsuit filed by Republican attorneys general. In that lawsuit, the administration argued that the entire Affordable Care Act should be deemed unconstitutional. A federal judge in Texas ruled in favor of the GOP attorneys general that the law was not constitutional because the 2017 Republican tax bill eliminated a requirement in the Obama-era health care bill that everyone carry insurance, known as the "individual mandate."

If that court's ruling is upheld by a higher court, as supported by the DOJ, the Affordable Care Act would be dismantled. Republicans have said, without providing specifics of how such a measure would succeed in a divided Congress, that they would quickly act to restore protections for people with pre-existing conditions.

--Alexander Mallin