There were 40.3 million people around the world living in slavery in 2016 — including 400,000 in the U.S., according to estimates in the 2018 Global Slavery Index that was presented at the United Nations by the Walk Free Foundation, a global organization combatting modern slavery.

Expand chart Data: Free Walk Foundation; Map: Kerrie Vila /Axios

Why it matters: The U.S. is also the top importer of items that are likely to have been products of slave labor in other countries. Andrew Forrest, founder of the Walk Free Foundation, told Axios that even places with comparatively fewer instances of modern slavery should be doing more and "are actually allowing slavery to exist."

The data on modern slavery includes situations of forced labor or forced marriage, but does not account for organ trafficking or the recruitment of child soldiers.

Between the lines: While conducting interviews with more than 71,000 people, Walk Free Foundation's researchers counted cases of slavery in the country where they were enslaved instead of their current residence. This led to much higher estimates in the United States, United Kingdom, Australia, Germany, France and other European nations compared to previous reports.

For example: In 2014, it was estimated there were 60,000 people in modern slavery in the U.S. on any given day. In 2016, that number was 400,000.

What to watch: Ivanka Trump has taken a personal interest in eradicating modern slavery, Forrest said, and spoke at the United Nations on the topic last year. Forrest hopes the report will convince President Trump to introduce a Modern Slavery Act, similar to what was passed in the U.K. in 2015.

It requires all businesses to publicly disclose what they are doing to stop the use of slave labor in their business and by their suppliers.

We’d be hard pressed to go to the supermarket to find a tin of tuna or to buy clothes the we felt assured weren’t cut by the hands of those in modern slavery.

— Fiona David, an author of the report, to Axios

By the numbers: