In the reporting period, Nigeria was by far the region's biggest exporter to the US - with $21.9 billion - almost entirely comprising energy-related products and almost all of it under AGOA.
The AGOA website says: "Nigeria, mainly through its oil exports, accounts for over half of all exports shipped under this trade programme."
Naumann said: "Nigeria was followed by Angola, with $8.7 billion, also almost entirely energy-related and under Agoa.
"Of the 37 AGOA beneficiaries, South Africa's exports to the US are by far the most diversified," he said.
Trade Law Centre for Southern Africa