Friday, 12 June 2009

Gigerenzer et al: What health statistics really mean

See this article in Scientific American Mind (this article also relates to some of the Chapter 3 material).

Thursday, 29 January 2009

Proportion dominance and the great flu pandemic

Chapter 8 (page 89) included a brief description of the phenomenon of "proportion dominance", whereby describing something as a proportion of something else can have a bigger effect on judgment that describing it in absolute terms. Thus, in an example given by Paul Slovic and colleagues, people were willing to pay more for a programme that was described as saving 98% of 150 lives than a programme described as saving 150 lives. This has implications for assessment of risk, as described below.

According to a review of a new book (details below) on the flu pandemic of 1918-19, proportion dominance (although not named as such) is the reason why we tend not to remember this terrible event. The pandemic killed 50 million people worldwide. Over 200,000 people in Britain died within a 9 month period. Even at the time, in Britain at least, there seems to have been a 'grin and bear it' attitude. And what people remember now is the first world war that came before, but killed fewer people than the flu pandemic.

However, despite the massive death toll from the pandemic the actual rate of mortality among those who contracted the flu was very low, just 2-3%. This proportion, obvious to everyone at the time, seems to be the reason for people's matter-of-fact attitudes towards the pandemic at the time. That, in turn, means that it has been barely remembered.

Another review of the same book notes how the British government responded to the pandemic at the time. The Chief Medical Officer of the Local Government Board encouraged people to go about their business as usual. However, the medical officer of health for Manchester advised quarantine and keeping one's distance from others. The latter strategy was far more effective than the first. This matters today, because pandemic influenza - although not the most probable threat to Britain - is judged the biggest risk because of the potential impact. And because the government's usual response to disaster is to recommend 'business as usual'.

The book referred to above is Living with Enza: the forgotten story of Britain and the Great Flu Pandemic of 1918, by Mark Honigsbaum (Macmillan, £15.99).

The first review referred to is by Michael Worboys in the January 2009 issue of the BBC History magazine.

The second review referred to is by Tony Barnett in the February 2009 issue of Prospect magazine.

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