How many were there when it mattered?

Estimating the sizes of crowds



150 000 people demonstrated in Hong Kong. 10 000 students protested in London against tuition fees. A million people lined the streets for the Royal wedding. Or did they? Do not believe what you are told, say Ray Watson and Paul Yip. Estimating the size of a crowd is a difficult business – even for those who actually want to get it right.