There are numerous challenges with respect to the eradication of slavery from international chains of commerce. Thus, no one knows exactly how many persons are enslaved in some aspect of international commerce. In addition, although slavery is known to exist in the supply chains of numerous products, the presence of slave-tainted material in any particular end product is unknown. For example, we know that some gold is mined by slaves, but slave-mined gold is thought to be a tiny percentage of the gold that is mined world-wide every year. We cannot walk into an electronics store and point to a laptop and state, with any degree of confidence, that that particular laptop contains slave-mined gold.
To further complicate matters, many slave-produced products are fungible, that is, they look the same as and can be exchanged with any other product of the same type. For example, slave-mined gold looks the same and has the same properties as non-slave-mined gold.