Two years ago Ghana’s statistical service announced it was revising its GDP estimates upwards by over 60%, suggesting that in the previous estimates about US$13bn worth’s of economic activity had been missed. As a result, Ghana was suddenly upgraded from a low to lower-middle-income country. In response, Todd Moss, the development scholar and blogger at the Center of Global Development in Washington DC, exclaimed: “Boy, we really don’t know anything!”
Here is more, by Morten Jerven. Here is another good paragraph from that article:
Let us be conservative and assume that the GDP in Nigeria merely doubles following the revision. This alone will mean that the GDP for the whole region increases by more than 15%. The value of the increase amounts to nothing less than 40 economies roughly the size of Malawi’s. The knowledge that currently there are 40 “Malawis” unaccounted for in the Nigerian economy should raise a few eyebrows.
I have just pre-ordered his forthcoming book Poor Numbers: How We Are Misled by African Development Statistics and What to Do about It.