This applies to people hired to escort cash in transit, patrol certain areas, conduct screening at airports and protecting VIPs.
The study features 11 countries including China, India, United States, Brazi, Russia and one African nation - South Africa.
South Africa has 487,058 private security workers compared to its 194,852 police officers. Right now, the private security industry in South Africa is said to be one of the largest in the world.
There are 8,626 registered companies, according to the Private Security Industry Regulatory Authority (PSIRA). Other reports say there are 450,000 registered active private security guards and a further 1.5 million qualified (but inactive) guards.
South Africa's booming private security sector has been attributed to the country's high levels of crime. In 2017, Daily Maverick, a South African online newspaper, reported that citizens spent R45 billion (N232.9 billion) annually on private security officials. This is over a third of what the government spent on the police force in 2016.
The country's private security sector has been criticised by many including Southern African Catholic bishops. During a conference in 2012, they released a briefing paper which argued that private security in South Africa "perpetuates fear", adding that the private security industry "only protects the select and privileged group that can afford to pay for security services" and "exacerbates the divide between the wealthy and the poor".
Private security in Nigeria
South Africa is not the only country experiencing a boost in its private security sector. In recent years, Nigeria's private security industry has also grown rapidly as it now offers services to international organisations, NGOs, embassies and businesses particularly the oil companies.
The Commonwealth of Nations reports that an independent 2005 study ('The Globalisation of Private Security, Country Report: Nigeria') found that there are between 1,500 and 2,000 private security companies (PSCs) in the country
Earlier this year, the National Bureau of Statistics announced that private security guards companies now employ no less than 828,502 Nigerians in 2018. In 2017, only 791,210 people were employed in this sector and 771,478 employed in 2016.
This makes security a major contributor to the Nigerian economy.