As of my last knowledge update in October 2021, specific and up-to-date statistics on the number of PhD holders in South Sudan can be challenging to find, as the country has faced significant challenges in education and data collection due to ongoing conflict and instability.
For the most accurate and current information, you may want to refer to reports from local educational institutions, the Ministry of Education in South Sudan, or organizations working in education and development in the region. If you're looking for recent statistics, checking academic publications or government reports published after 2021 would be beneficial.