The ignorance of the Ipsos Mori Ignorance Index

A number of news outlets and otherwise sophisticated blogs are reporting on the Ipsos Mori "Index of Ignorance", where the polling group purports to gather data about how people misunderstand and ‘overestimate’ proportions of various values in their societies, such as the percentage of Muslims, or the rate of teen pregnancy.  For instance, British people estimated that 21% of the population of Britain is Muslim, where the actual figure is about 5%.  The poll goes so far as to rank these countries based on their ‘ignorance’.

There is a news story here, but it is the exact opposite of the reported one: people are shockingly good at estimating the proportion of events in their countries. I guess I can’t blame Ipsos for getting it so wrong, because in order to see what’s going on, you need a basic understanding of psychophysics.

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