“Although it is speculative it seems appropriate to estimate that up to 1.5 million ethnic minorities—equivalent to just under 1 in 6 adult members of a predominantly Muslim minority group in Xinjiang—are or have been interned in any of these detention, internment and re-education facilities, excluding formal prisons,” Zenz said in March. “There is virtually no Uyghur family without one or more members in such detention, and a rising number of Kazakhs and other Muslim minorities are likewise affected.”

Updated satellite images show the camps expanding in size, alongside rising regional security finances and higher arrest numbers. Meanwhile, a Wall Street Journal report found that that numbers of registered Uyghur Muslims (paywall) living in Xinjiang have decreased for the first time in decades.

This May, the US Defense Department accused China of running “concentration camps” with up to 3 million Muslims imprisoned—a remark that drew censure from one of the most scrupulous documenters of the detentions.

The new number by the US is one of the higher numbers used by a government or international organization thus far. Last year, the State Department’s annual report on religious freedom (pdf) used estimates of 800,000 to more than 2 million Muslims in detention, citing media and NGOs.

Zenz said he believes the latest US figure adds together two different populations—those imprisoned and those who are attending part-time “re-education” programs while continuing their daily lives in Xinjiang.

“This must be distinguished from internment in camps, which is a much more serious matter,” Zenz said. “I consider speculations about part-time re-education figures to be highly problematic. Lumping them together with full internment is even more problematic.”

Academics, journalists, and human rights organizations have worked with the limited but specific evidence—amid clear perils and pitfalls on their validity—to bring forward strong estimates. Inflated numbers that aren’t grounded in careful estimates and concern for human rights risk jeopardizing their hard work.

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