Forced labour is not to be confused with bonded labour. Bonded labour is, for the most part, connected to debt but forced labour has a different general foundation. It can be described as any labour or any service which people are forced to do against their will. It comes with some form of threat of punishment or deprivation. There are not many situations of slavery that do not involve some form of forced labour.
As with most people caught up in slavery, poverty and vulnerability are a common factor. With large populations living in poverty it is easy to understand how forced labour from the point of view of those caught in it is need driven. Pictures of people working in sweatshops making goods for little income to be sold at great profit by Western companies help to raise awareness of this pernicious industry. Women and girls are most certainly more vulnerable than men and boys and shamefully some 25% of those caught in forced labour are children. Sometimes it can be because of your situation at birth. For example the 'untouchables' or Dalits in India; religious minorities are also often easy targets to enslave with forced labour. It is not only in the context of poverty that forced labour thrives but also a lack of sustainable employment and education, corruption or lack of incentive to enforce the law.
This is a global problem and recent estimates by the International Labour Organisation have come up with the following estimates, which are almost certainly growing daily.
Ending forced labour and modern-day slavery in global supply chains requires binding legislation, rather than corporate self-regulation. While corporate self-regulation might gradually reduce forced labour and modern-day slavery, binding legislation is necessary to end it in global supply chains.