Klein, N. (2011). Measuring the Potential Output of South Africa. IMF African Department Paper No. 11/2. Washington: International Monetary Fund.
Klein estimates potential growth by several methods and finds it “very modest, at slightly below 1 percent” in 1985 to 1994, which he attributes to “the high economic costs associated with isolation of the apartheid regime.” Estimated potential growth rises after 1994. The wiki cites the estimate in South Africa on the Curve as the main quantitative reading of governance costs in the late National Party period.