Have you ever heard the term wage slavery? It is used to compare certain types of low-paid work to slavery. 
I have heard of that. Who is the biggest user of slaves today?
Slavery in the 21st century
Contemporary slavery, also known as modern slavery or neo-slavery, refers to institutional slavery that continues to occur in present-day society. Estimates of the number of slaves today range from around 21 million to 46 million, depending on the method used to form the estimate and the definition of slavery being used. The estimated number of slaves is debated, as there is no universally agreed definition of modern slavery, those in slavery are often difficult to identify, and adequate statistics are often not
of wage slavery which refers to a situation perceived as quasi-voluntary slavery, where a person's livelihood depends on wages, especially when the dependence is total and immediate. It is a negatively connoted term used to draw an analogy between slavery and wage labor by focusing on similarities between owning and renting a person. The term "wage slavery" has been used to criticize economic exploitation and social stratification, with the former seen primarily as unequal bargaining power between labor and capital (particularly when workers are paid comparatively low wages,