Statistics South Africa has decided to include illegal and underground economies, when calculating the country's gross domestic product.

Cannabis farming will now form part of the agricultural sector while prostitution falls within the personal services sector.

It is understood the inclusion of illegal economies into GDP is already a global practice.

"Theoretically it is absolutely correct to include as much of the production in the economy as possible when you calculate GDP growth, so theoretically there is nothing wrong with including things like dagga sales in your economic statistics," says Efficient Group Economist Dawie Roodt.

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