South Africa has the world's seventh highest number of prisoners - outranking countries with up to nearly five times our population.
The World Prison Brief places South Africa's total of 166 267 prisoners after the United States (2,3-million inmates), China (1,6-million), Russia (888 014), Brazil (419 551), India (358 368) and Mexico (217 436).
The populations of the top six countries on the list range from 104-million in Mexico to 1,3-billion people in China - with a combined total of 3-billion people.
South Africa has just 47,8-million citizens.
Gideon Morris, director of the Cape Town-based Judicial Inspectorate of Prisons, said: "Our rate of imprisonment is much higher than any other country in Africa, as well as one of the highest in the world.
"We use the quick fix: throw them into prison."
The latest figures show that it costs R69 000 annually to house a prisoner.
Sixty-eight percent of all sentenced prisoners are serving a sentence of five or more years.
And inmates serving life sentences rose from 793 in 1999 to a current figure of 7 574.
"One must look at the direct cost to the taxpayer," said Morris. "In 1997 we were spending R3,7-billion annually on running prisons. Last year we spent almost R12-billion."
The World Prison Brief is published by the International Centre for Prison Studies at Kings College in London.
It lists South Africa and Botswana with Africa's highest ratio of prisoners to total population, followed by Namibia and Libya.
However, South Africa sits at number 24 worldwide with 348 prisoners for every 100 000 of its people.
The US again heads the list with 751 prisoners for every 100 000 of its national population.
South Africa had the most prisoners in Africa, while Rwanda, the second highest, had half the number, with 82 000 behind bars.
Nigeria, the continent's most densely populated country with 136-million people, has 39 438 prisoners. Of these 65 percent have yet to be sentenced.
Zambia had the world's highest occupancy rate, with prisons that are 330,6 percent full.
South Africa's occupancy rates are 145 percent and 177 percent in Gauteng, said Morris. Mthatha Maximum is the most overcrowded, at 329 percent.
The country's biggest prison population is at Johannesburg Medium A, which is meant to house some 2 630 people but has 6 973 unsentenced prisoners.
"The conditions there are horrific," said Morris.
"The infrastructure simply cannot cope with demand."
The prison population was 165 987 on January 31 - slightly lower than the World Prison Brief figure recorded a month earlier.
Morris said an average of 45 079 people passed through prisons as unsentenced prisoners every two months in 2006.
"They're arrested, they go to prison pending trial. The case will be withdrawn or thrown out of court, or they will be found not guilty."
There are also 11 500 people in SA's jails simply because they are too poor to pay for bail.
Overcrowding, gangs, smuggling, poor hygiene and lack of security in South African prisons was highlighted in the Office of the Inspecting Judge of Prisons' 2006-2007 annual report.
Inmates in critically overcrowded prisons had less than 1,2m² - the size of an average office table - in which they slept, ate and spent 23 hours a day.
Many prisons had open communal toilets shared by 20 to 30 adults.
It was also not uncommon to find prisoners forced to share bed space, sleep on the floor or under beds, in toilets and showers.
Lack of access to sufficient exercise was also found.
At some prisons built out of corrugated iron, temperatures exceeded 40ºC. Six Eastern Cape prisons had no running water.
Unsentenced children came into daily contact with adults despite being separated - making them extremely vulnerable to intimidation, violence and rape.
Children were also the favourite target to be recruited by gangs, and often had to perform sexual acts.
The number of women in prisons was 2,2 percent - lower than the 7 percent international norm.
Of total prisoners, 32 percent were pre-trial or remand inmates and figures have recently risen.