I don't believe that. Chinas prison stats are around 1.69mil (which is oddly on par with the US - per capita not taken into consideration). However, per the Global Slavery Index, there's an estimated 5.8 million people enslaved there. And we know that there were over 1 million Uyghur Muslims, and we really don't even know the extent to which that is happening either.

I'd be willing to bet that there's a lot more slave/prison labor going over there than even we realize.

This post has so many controversial aspects:

• There are no real numbers from china, how many people are actually imprisoned or what even means imprisoned. For example the Uyghurs are not Prisoners in Prison but "Citizens in reeducation camps"- what is a lie. Pictures show they are indeed imprisoned . China is fudging these numbers like the economy numbers at a grand scale.
• China is able to force people to work in certain regions or cities. They have a complex system on how to channel work by prohibiting living-, healthcare- and pensions-systems to citizens based on their location and citizens need to apply for changes to these systems to be able to work in other regions.
• China - as an authoritarian regime - can force every prisoner to work if they deem it useful. The US has different rules for penal labor, but not make prisoners work like china. The US has a much different landscape.
• China undercut every good, in every sector (except some high tech sectors) based on their vast (forced) workforce but also in the strategic sense. They act like Uber (or is Uber acting like China?) in the sense, that their strategy in the last 4 decades was to undercut e.g. Steel-Production for their own advances, but also to cripple the industries in the US and the West in general to come out as the sole supplier for these products and services to then control the prices (like Uber). The US Steelworker Industry is practically gone by now. They did the same with raw-materials and lately with Solar, where they undercut the European (German) markets, to cripple it and control the production/income/spread.

Instead, China uses their prison population to bolster their organ transplant market.

Edit: I wonder if the people who downvoted realise that China admitted they had been harvesting organs from prisoners but claimed it was voluntary and that they were stopping. Meanwhile, the exponential growth of their transplant industry continued beyond 2014.

Cool, I was just thinking the answer to this problem was either 'both sides' or 'what about'.