In the modern world the concept of "slavery" is generally used in one of two ways: to reference slavery in the past, or as a metaphor for bad treatment in the present. However, literal slavery still exists in the world even if it hides under different names.
In which case, assuming even the rough accuracy of 27 million, there are likely more slaves in the world today than there have been at any other time in human history. For some quick perspective on that point: Over the entire 350 years of the transatlantic slave trade, 13.5 million people were taken out of Africa, meaning there are twice as many enslaved right now as there had been in that whole 350-year span.
It's a sobering read. Slavery isn't just a thing of the past or a euphemism for exploitative conditions. Literal slavery still exists.