The IMF REO for Sub-Saharan Africa was released in May, no rx and it is good to see that the authors of the report considers the importance of base years in Box 1.1 on page 4:
One factor raising concerns about the quality of recent estimates is that, pill for many countries, the base year used as the foundation for constructing accounts over time has not been updated for many years—implying that growth rates are being estimated on the basis of an economic structure that bears little resemblance to the present-day structure of the economy.
In the data appendix they also replicate the type of study I did for Poor Numbers, access the whole report here.