(CNN) The second night of the first 2020 Democratic presidential debate continued with 10 candidates , including three of the top polling leaders in former Vice President Joe Biden, Sen. Bernie Sanders of Vermont and Sen. Kamala Harris of California.

The candidates tackled health care, immigration, race issues, taxes and the economy.

Iraq War troop withdrawal

Former Vice President Joe Biden, asked about his vote for the Iraq War and his judgment on taking the US to war, touted the withdrawal of US troops from Iraq in 2011.

"Once (President George W. Bush) abused that power, what happened was we got elected after that ... I made sure ... (President Barack Obama) turned to me and said: 'Joe get our combat troops out of Iraq.' I was responsible for getting 150,000 combat troops out of Iraq, and my son was one of them."

Facts First: Biden is correct that he oversaw the withdrawal of US troops from Iraq in 2011. But he left out a key point -- three years later, US troops returned to Iraq to fight ISIS, which rose to power in the vacuum left, in part, by the withdrawal of American forces.

Biden voted to authorize military intervention in Iraq in 2002 and later became a critic of the Bush administration's handling of the war. His son, Beau, also deployed to Iraq for a year in 2008, serving in an administrative post with the 261st Signal Brigade.

The withdrawal of roughly 150,000 US combat troops from Iraq became a major part of Biden and President Obama's election platform in 2008 and ultimately, the last American convoy left the country in December 2011.

In 2014, the US sent a much smaller contingent of a few thousand soldiers back to Iraq as part of the campaign against ISIS after the terror group rose to power and claimed a significant portion of territory both in Iraq and Syria.

-Zachary Cohen

Top 1% seeing a $21 trillion wealth increase

Vermont Sen. Bernie Sanders hammered home a familiar theme for him, saying that the middle class is stagnating, while the richest Americans are adding to their wealth.

"In the last 30 years, the top 1% has seen a $21 trillion increase in their wealth," he said.

Facts First: The top 1% of households saw their wealth grow by $22.3 trillion on an inflation-adjusted basis, according to Federal Reserve data.

Matt Bruenig, the founder of the left-leaning People's Policy Project, earlier this month also released an analysis based on Federal Reserve data, which tallies Americans' wealth. He adjusted it for inflation, but removed the value of certain possessions, such as cars and refrigerators, and found a $21 trillion increase in wealth for the top 1% from 1989 to 2018, while the wealth of the bottom 50 percent dropped by $900 billion during the same timeframe.

-Tami Luhby

Chinese investment in AI

South Bend Mayor Pete Buttigieg said that China is investing massively in artificial intelligence.

"China is investing so they could soon be able to run circles around us in artificial intelligence, and this president is fixated on the China relationship as if all that mattered was the export balance on dishwashers."

Facts First: Buttigieg's assertion that China is prioritizing artificial intelligence is true, but the Trump administration has proposed significant investments as well.

The Chinese government has outlined an aggressive plan to become a world leader in artificial intelligence by 2030, according to the New York Times . One Chinese city, Tianjin, announced last year it will establish a $16 billion fund to support the development of AI, according to Reuters . And according to CNBC , Chinese state media reported last year that the country will build a $2.1 billion development campus that will accommodate 400 businesses and produce an estimated $7 billion in annual productivity.

China accounted for 48 percent of all AI-related venture capital in 2017 — outstripping the United States for the first time, according to CB Insights , a venture funding research firm.

According to a Bloomberg Government review of the Trump administration's fiscal 2020 budget request, federal agencies are expected to spend $850 million on AI research. Over the same timeframe, the Pentagon could spend as much as $4 billion on R&D for machine learning and AI.

-Brian Fung

Biden on his past praise of segregationist senators

Former Vice President Joe Biden and California Sen. Kamala Harris had a tense exchange over Biden's past praise of some senators who supported segregation and his opposition to busing.

"It was hurtful to hear you talk about the reputations of two United States senators who built their reputations and career on the segregation of race in this country. It was not only that, but you also worked with them to oppose busing," Harris said.

Biden responded, "I do not praise racists. That is not true."

Facts First: This exchange needs context. Biden does have a history of praising senators who supported segregation, but in several instances he claimed they changed on the issue of civil rights.

Biden's campaign was riled last week when he cited two segregationist senators and as examples of colleagues he could work with during an era where "at least there was some civility" in the Senate. Biden did not praise either of the men, but he does have a history of praising several senators who supported segregation and opposed the Civil Rights Act -- though not for their positions opposing civil rights.

Biden praised then-Mississippi Sen. John Stennis, a staunch segregationist as a "hero" and "the rockbound integrity of the United States Congress" in the 1980s. Biden called Stennis "a hell of a guy" in 2008.

Biden also has praised South Carolina Sen. Strom Thurmond, who ran for president as a segregationist in 1948 as a Dixiecrat. In 1993, Biden spoke at Thurmond's 90th birthday and praised him by comparing him to Confederate General Robert E. Lee.

Biden has claimed both Stennis and Thurmond changed with the times. When Thurmond died, Biden said he did not believe the senator was racist at his core.

In his Senate farewell address in 2009, Biden said he became friends with Stennis, Thurmond and Mississippi's James Eastland despite opposing their views on civil rights.

"I never thought I'd develop deep personal relationships with men whose position played an extremely large part in my desire to come to the Senate in the first place to change what they believed in -- Eastland, Stennis, Thurmond. All these men became my friends," Biden said

-Andrew Kaczynski

Assault-style weapons ban

Vermont Sen. Bernie Sanders said in 1988 he supported an assault-style weapon ban and lost.

"In 1988 when it wasn't popular, I ran on a platform of banning and in fact lost that race for Congress," Sanders said.

Facts First: This is true. Sanders supported a ban on semi-automatic rifles in 1988 and he did lose that race.

According to the Burlington Free Press and The Washington Post, Sanders did support an assault-style weapon ban during his first run for the House of Representatives, though it's unclear how much it contributed to his defeat.

-Andrew Kaczynski

Biden's busing record

Sen. Kamala Harris and former Vice President Joe Biden had a testy exchange on race and school busing. It began with Harris referencing Biden's recent comments about working with segregationist senators, and ended with her personal story of benefiting from busing, a policy she criticized Biden for opposing.

"And it was not only that, but you also worked with them to oppose busing. And there was a little girl in California who was part of the second class to integrate her public schools and she was bused to school every day. And that little girl was me."

Biden shot back claiming Harris' comments were "a mischaracterization of my position across the board." Biden said he opposed busing mandated by the Department of Education but that he would have allowed localities to bus students should they choose to do so.

Facts First: Biden was a vocal opponent of federally-mandated busing. His remarks in the 1970s broadly denounced busing programs claiming they were bad for local communities.

In 1978, Biden co-sponsored and strongly advocated for legislation that would have limited the ability of federal judges to compel school districts to integrate public schools by busing black students to white areas and vice versa. He particularly solicited the support of segregationist Mississippi Democrat James Eastland, writing in 1977, "I want you to know that I very much appreciate your help during this week's committee meeting in attempting to bring my anti-busing legislation to a vote."

Biden says he would allow busing under certain circumstances. In cases where a school system has been racially segregated by gerrymandering district lines or by other legalistic means, Biden said he supported desegregation by any legal means at hand -- including busing.

In 1975, Biden supported an amendment offered by North Carolina Republican Senator Jesse Helms that would have made busing much more difficult in all jurisdictions by prohibiting the Department of Health, Education and Welfare from collecting information needed to identify segregated school systems.

However, neither piece of legislation would have explicitly prohibited Berkeley, where Harris went to school, from choosing to bus black students into majority white schools or vice versa. Berkeley was one of the first cities to adopt a busing program in 1968.

After the Helms amendment failed , Biden offered a provision that would've prevented federal funds from being used to require any school to assign students or teachers by race.

Biden said he supported school integration by other means but opposed busing because he thought it had a negative impact on communities.

-Lydia DePillis, Daniel Dale and Andrew Kaczynski

Requests to detain undocumented immigrants

Sen. Kamala Harris said that she told local sheriffs in California when she was the state's attorney general that they could buck certain requests to detain undocumented immigrants made by federal immigration officials -- a progressive policy that is still fought for today by immigration activists.

Facts First: This is true.

In 2012, Harris issued an "information bulletin" to law enforcement agencies in the state saying that they were not required to fulfill detainer requests from US Immigration and Customs Enforcement, or ICE.

At the time, the American Civil Liberties Union wrote that her statement "should finally put to bed any lingering doubt that immigration detainers are voluntary requests" and noted that a better solution would be the passage of statewide legislation.

-David Shortell

Green New Deal

Former Colorado Governor John Hickenlooper criticized a liberal policy proposal, saying "if you look at the Green New Deal, which I admire the sense of urgency and how important it is to do climate change, I'm a scientist, but we can't promise every American a government job."

Facts First: This is almost true. While the Green New Deal does guarantee people jobs, it doesn't specify they'd be government jobs.

The Green New Deal is a proposed bill that is more a list of ideas than a hyper-detailed proposal. This 14-page piece of legislation touches on a wide range of topics including cutting carbon emissions and switching power generation to 100% renewables. It also does promise everyone in the US a job, but it does not specify that it would be with the government.

Specifically, the legislation says it is "guaranteeing a job with a family-sustaining wage, adequate family and medical leave, paid vacations and retirement security to all people of the United States."

The bill also promises workplace safety laws, paid vacations, family and medical leave and it offers discrimination protections.

-Jen Christensen

America's wealth gap

Colorado Sen. Michael Bennet claimed that 160,000 families that make up the top 0.1% have the same wealth as the bottom 90%.

Facts First: This is correct, according to one study.

There are several ways to measure wealth in America, and none of them are perfect. However according to at least one analysis from economists, this statistic is true.

Emmanuel Saez and Gabriel Zucman at the University of California-Berkeley sent a letter to Massachusetts Democrat Elizabeth Warren -- who often touts this comparison of wealth -- with their estimate of how much revenue her 'ultra wealth tax' would generate.

In the letter, they wrote that the 0.1 percent own about 20% of the nation's wealth. The bottom 90% own about 25%.

-Holmes Lybrand and Donna Borak

CORRECTION: This post has been updated to correct the bottom-line conclusion about the statistic Bennet cited

China tariff cost

South Bend Mayor Pete Buttigieg claimed that because of President Donald Trump's tariffs on China, "Americans are going to pay on average $800 more a year."

Facts First: Buttigieg is slightly underestimating the cost of Trump's China tariffs, according to one paper published by the Federal Reserve Bank of New York.

The study found that Trump's latest tariff escalation -- which raised the rate from 10% to 25% on $200 billion of Chinese goods -- could cost a typical household $831 a year. That's in addition to the $414 cost that could be incurred by the earlier rounds of tariffs imposed during 2018.

-Katie Lobosco

Migrant children dying in US custody

New York Sen. Kirsten Gillibrand claimed that seven migrant children have died in US custody during the Trump administration.

"He's torn apart the moral fabric of who we are, when he started separating children at the border with their parents, the fact that seven children have died in his custody," Gillibrand said.

Facts First: Gillibrand is correct.

At least seven children migrating to the US from the southern border have died in US custody since 2018, according to news reports and government statements

-Maegan Vazquez

Undocumented immigrants paying taxes

South Bend Mayor Pete Buttigieg said, "There are undocumented immigrants in my community who pay sales taxes and pay property taxes directly or indirectly."

Facts First: It's true that undocumented immigrants pay taxes.

Undocumented immigrants pay billions in taxes each year, even though they do not have Social Security numbers. They file using what's known as an Individual Taxpayer Identification Number.

"Most experts believe that the vast majority of tax returns filed with ITINs today are filed by undocumented immigrants," according to the Bipartisan Policy Center , a Washington-based think-tank. That method is also used by some non-citizens who are legal immigrants to the US.

In 2015, according to the IRS, 4.35 million tax returns were filed using ITINs, accounting for more than $13.6 billion in ta

xes.

-Priscilla Alvarez.

Swalwell quotes Biden on passing the torch

In arguing for a candidate from a new generation to be the Democratic nominee, California Rep. Eric Swalwell quoted then-Sen. Joe Biden speaking in 1987 at the California Democratic convention.

"I was six-years-old when a presidential candidate came to the California Democratic convention and said, 'It's time to pass the torch to a new generation of Americans.' That candidate was then-senator Joe Biden. Joe Biden was right when he said it was time to pass the torch to a new generation of Americans 32 years ago. He's still right today. If we're going to solve the issues of the nation, pass the torch. If we're going to solve the issue of climate chaos, pass the torch. If we are going to solve school violence, pass the torch."

Facts First: Biden did say this February 3, 1987, at the California Democratic convention and it was a part of his Biden did say this February 3, 1987, at the California Democratic convention and it was a part of his stump speech during his 1988 presidential campaign and in appearances during the previous year. He was quoting John F. Kennedy and talking about how it made him feel at the time.

"Remember how you felt when you heard let the word go forth, from this time and place, that the torch has been passed. Passed to a new generation of Americans," Biden said, quoting Kennedy's inaugural address

-Andrew Kaczynski

Undocumented immigrant contributions to Social Security

Former Vice President Joe Biden said, "(Undocumented immigrants) in fact contribute to the well-being of the country, but they also for example increase the lifespan of social security. Because they have a job, they're paying a social security tax. That's what they're doing. It's increased the lifespan."

Facts First: This is true.

Undocumented immigrants often pay into the Social Security system through payroll taxes, but typically do not receive benefits. According to a 2013 report by the Office of the Chief Actuary of the Social Security Administration, in 2010, undocumented immigrants paid about $12 billion more into the system than they received.

That could extend the period of solvency for the Social Security trust funds, which are currently projected to be depleted in 2035.

-Lydia DePillis

Amazon's taxes

Andrew Yang claimed that Amazon pays "literally zero in taxes." "Oh, so, it's difficult to do if you have companies like Amazon, trillion-dollar tech companies paying literally zero in taxes while they're closing 30% of our stores."

Facts First: When it comes to taxes, the picture is more complicated than Yang claims. Amazon pays state taxes and has also paid federal taxes in the past.

The Wall Street Journal reported recently that Amazon's overall tax rate from 2012 through 2018 was 8%.

"From 2012 through 2018, Amazon reported $25.4 billion in pretax US income and current federal tax provisions totaling $1.9 billion," the Journal reported. "That is an 8% tax rate — low, but not zero or negative. Looking back further, since 2002, Amazon has earned $27.7 billion in global pretax profits and paid $3.6 billion in global cash income taxes, a 13% tax rate."

Amazon's SEC filings in 2017 showed it did not expect to owe any federal tax, and in fact expected to get a $137 million refund from the federal government. It did, however, say it expected to pay $211 million to states.

More recently, in February, an analysis of Amazon corporate filings by the Institute on Taxation and Economic Policy found that the company got a rebate of $129 million for tax year 2018.

Analysts say Amazon was able to whittle down its tax liability by taking advantage of tax credits and deductions.

-Brian Fung

Tax benefits

Bernie Sanders claimed "83% of your tax benefits go to the 1%."

Facts First: This is incorrect. For the 2018 tax year, the top 1% was estimated to have received 20.5% of the benefits from the tax cuts, according to the non-partisan Tax Policy Center.

Some estimates say that if certain tax cuts are not reapproved by Congress after they sunset in 2027, 83% of the benefits would go to the top 1%.

President Donald Trump's tax reform law passed in December 2017 included tax cuts for corporations as well as individuals -- but while the benefits for business were permanent, the individual taxpayer cuts will expire by 2027. If Congress does nothing to extend them, the top 1% will at that point receive roughly 83% of the tax cut benefits, according to the Tax Policy Center

-Holmes Lybrand

Trump's tax bill

California Sen. Kamala Harris claimed that the tax bill signed by President Donald Trump benefits major corporations and will contribute at least $1 trillion to the US debt.

Facts First: This is true. The Congressional Budget Office estimated that the 2017 tax act would add some $1.9 trillion to the federal deficit over the next decade.

CNN has previously reported that the Republican tax reform bill passed in 2017 included tax cuts for corporations as well as individuals -- but while the benefits for business were permanent, the individual taxpayer cuts will expire by 2027. If Congress does nothing to extend them, the top 1% will at that point receive roughly 83% of the tax cut benefits, according to estimates from the nonpartisan Tax Policy Center.

Last year, the Congressional Budget Office projected that the Republican tax bill would add $1.9 trillion over the course of 10 years.

-Maegan Vazquez and Holmes Lybrand

America's wealth gap

Sen. Bernie Sanders blasted the rich for taking advantage of America, saying that three people own more wealth than the bottom half of the nation.

Facts First: It's true that the three richest Americans have more wealth than the bottom half of the nation, according to a 2017 study by the left-leaning Institute for Policy Studies.

Bill Gates, Jeff Bezos, and Warren Buffett had more combined wealth ($248.5 billion) than the 160 million people on the lower rungs of the wealth ladder, according to the study

The institute used data from the 2017 Forbes 400 list and the Federal Reserve's 2016 Survey of Consumer Finances.

-Tami Luhby

US homeless population

In calling for change, Bernie Sanders said, "500,000 people are sleeping out on the streets today."

Facts First: Sanders is basically correct here. While the number of people experiencing homelessness fluctuates in the United States, the most recent government tally lines up with Sanders' claim.

According to the federally mandated Point in Time Count conducted every year by HUD to count the nation's homeless population, there were 552,830 people experiencing homelessness on a single night in December 2018.

-Lydia DePillis