Inside Amazon’s rankings
Amazon updates its rankings of book sales every day, but the conversion from the Amazon rank to the actual level of sales is a closely guarded secret. Didier Sornette and colleagues at the Institute of geophysics and planetary physics at UCLA have recently carried out a detailed study of rankings on the website. They estimate that the book ranked ten in sales on amazon.com sells about 100 a day and rank number 100 around 30 a day. But sales fall away rapidly, with rank 1,000 selling some ten a day and rank 10,000 just two.
Way down in the long tail—an online retailing concept discussed elsewhere in this issue (see p65)—the book at rank 100,000 sells about one copy a week. But the unfortunates at rank 1m have total sales of just 15.
The Sornette study identifies two typical patterns of bestsellers. One bursts into the top rank overnight. For example, on 4th June 2002, the New York Times published a piece saying that readers interested in having a “youthful post-menopausal body” should buy Strong Women Stay Young by Miriam Nelson. On 5th June, the book jumped from a rank in the 2,000s to six. At the same time, Heaven and Earth by Nora Roberts finally made it into the top rankings, after a steady rise over four months with little media hype.
How dangerous is the US? The appalling murders of the Amish schoolgirls has led to a flurry of reports about the culture of violence and guns in the US. Yet America is becoming a much safer place to live. The homicide rate was around 100 per million population in the early 1970s, and it has now declined to some 60 per million. In contrast, the British rate is rising. In the early 1970s, the homicide rate in Britain was 8 per million and it is now 15 per million. So 30 years ago, homicide rates were 12 times higher in America than in Britain, and they are now 4 times higher. Of course, the aggregate statistics conceal huge geographical differences. In three cities in particular—Washington DC, Detroit and Baltimore—the homicide rate is close to a staggering 400 per million population. Interestingly, way back in 1900, when anyone of any age could own a gun in the US, homicide rates were much lower, at only 10 per million.
When it comes to violent…