It ain't easy being a Nigerian census taker. Once you've crossed the desert on a snorting camel and dodged the rebels seeking to attack you with acid and machetes, you still might not get the information you're after.
It's considered bad luck to ask a Yoruba how many children the family has. Asking a herdsman about his cows or camels likely will get you shown the door. And what is a male census worker to do when Muslim women are home alone? [Link]