I downloaded their report and they seem thorough. It appears Nyandarua has been really growing - together with Elgeyo Marakwet. Nyandarau is doing well in Agriculture (33 to 40% of potato production - 2nd most important food crop in kenya now), I guess horticuluture (vegetables) and dairy - so their fortunes maybe changing. Their GCP has risen from 85B to nearly 250B.
Honestly I don't know how they add up Nyandarau production or any county to such eye popping figures. I'd imagine potato production nationally at maybe 1B dollars...so that would give Nyandarau maybe 40B? Maybe Dairy they'd get a share of say 20-40B? Horticulture maybe another 20-40B? And other crops maybe 20-40B - total of 100-150B - and the rest of sectors would then add an extra 100-150B?
Obviously it doesn't capture that fact that farm gate prices of whatever Nyandarau produce is a far crying from what obtains in the market and hence the widespread poverty there.