What percentage of the migrant labourers are slaves? The article seems to site examples of abuse (no doubt existing and still horrible), but seems to extrapolate them into the norm.

I'm skeptical that it is the majority of cases since migrants send a huge amount of remittances to their home countries and a lot of people depend on this labor. In the article it was mentioned that a builder gets paid $28k per year which is still great for the majority of the world.

This is one article on the dependence of some areas of India to remittances from the Gulf states: https://economictimes.indiatimes.com/nri/forex-and-remittanc...