“Mr Kale must be creative. When people are asked how much they earn, suspicion of authority makes them underestimate. Ask them how much they spend, however, and, chest puffed up, they will give a much higher number. In surveys, getting the question right matters.

Mr Kale cannot take much at face value. He even checks his own fieldworkers’ movements through GPS. Otherwise, staff may be tempted to sit at home and make up numbers rather than slogging around the country.

It was under Mr Kale that Nigerians woke up one day in 2014 to discover that their economy was 89 per cent bigger than previously imagined, making it Africa’s largest.”

http://www.ft.com/cms/s/0/68b6253a-df0b-11e5-b072-006d8d362ba3.html#axzz41jVD8msf

http://www.ft.com/cms/s/0/3b3b81d2-dfcd-11e5-b67f-a61732c1d025.html#axzz41jVD8msf