According to financial disclosures and tax returns provided by the campaign, former Vice President Joe Biden and his wife Dr. Jill Biden have earned more than $15 million since 2016.

The majority of the income comes from book deals and speaking engagements, with the Bidens earning around $9.5 million in 2017, the year after Biden left office. That year, the Bidens donated more than a million dollars to charity, according to the documents.

On the campaign trail, Biden regularly touts his middle-class bona fides by referring to his nickname "Middle-Class Joe," a nod to his more modest upbringing in Pennsylvania and Delaware. He has centered his campaign on fighting for the middle class, even though he may now be one of the wealthiest Democrats in the presidential field.

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Since leaving office, both Bidens have worked as college professors. Jill Biden taught at Northern Virginia Community College and made more than $180,000 in two years, while her husband was named the "Benjamin Franklin presidential practice professor" at the University of Pennsylvania, earning more than $775,000 in two years.

The couple paid a roughly 33 percent federal income tax rate in the past two filing years.

Most of the former vice president's speaking fees were to promote his book "Promise Me, Dad," but at least 17 were additional appearances. In total, this resulted in more than $4 million of income. During this time, Jill Biden pulled in more than $700,000 for speaking engagements.

Joe Biden was paid more than $100,000 per speech at some events, organized by groups such as the Jewish Community Center of San Francisco and at universities including Long Island University, Vanderbilt University, and Brown University, among others.

A list of charitable donations shows that a year before the International Association of Firefighters (IAFF) endorsed Biden for president in April 2019, the Bidens donated $25,000 to the IAFF Foundation and $10,000 to another fire department. A Biden spokesman indicated on Twitter after the documents' release that this donation was for the foundation's disaster relief fund.

In 2017, the Bidens also gave $180,000 to the United Jewish Federation of Chicago, $120,000 to the Delaware Center for Justice, Inc., $100,000 to the Joseph Biden Foundation and $150,000 to the children's tragedy assistance foundation named for their late son, Beau Biden.