Rule of Thumb Method
Sir Ashby had been requested in 1960 by the Government of Nigeria to submit a report on manpower development in Nigeria. In doing so, in the absence of reliable micro level data, Ashby assumed that high level manpower should grow twice as fast as the target of economic growth. Likewise, second level manpower should grow three times as fast as the target of economic growth. This ratio was suggested on the basis of the experience that high level manpower categories like engineers, doctors and other professionals will always be skewed at the top as compared to their important junior level functionaries like technicians, para-medical and other supporting staff at lower levels.
However, the relation of the production of manpower to targeted economic growth did not take shape in expected ways. This was because the assumptions made were not based on hard data. Hence it came to be known as the ‘Rule of Thumb’ method.