The economies of Persian Gulf countries expanded between 2005 and 2015. This encouraged millions of migrants to move to the Middle East. Overall, the number of non-displaced, international migrants living in the Middle East grew by 61% between 2005 and 2015, from about 19 to 31 million. Sources of worker include Bangladesh, Ethiopia, India, Pakistan, the Philippines, and Yemen. Two thirds of these migrants are in Saudi Arabia and the United Arab Emirates (source).
The Gulf countries use the “kafala” system of employing migrant workers. The kafala system binds these migrant workers in a direct relationship with their private sponsoring recruiters or employers to a particular job for a specific period of time. The system codifies the centrality of sponsors, as workers cannot change their employment or leave the country without approval.
The United Nations in 2014 told Qatar the kafala system led to dangerous working conditions and exploitation. Hundreds of foreign workers have died in the massive construction buildup underway for the 2022 World Cup, with estimates that as many as 4,000 workplace deaths could occur. In 2015, Qatar had 1.7 million migrant workers, up from 600K in 2005.
In late 2018 Qatar passed an act which allows some migrant workers to leave; Human Rights Watch criticized it.
Most recently, as their economies have cooled, Gulf countries have been expelling migrants. This has impacted the flow of remittances back to source countries.