Saturday, April 23, 2011

The $23.7 million book on Amazon

A few weeks ago a postdoc in my lab logged on to Amazon to buy the lab an extra copy of Peter Lawrence’s The Making of a Fly – a classic work in developmental biology that we – and most other Drosophila developmental biologists – consult regularly. The book, published in 1992, is out of print. But Amazon listed 17 copies for sale: 15 used from $35.54, and 2 new from $1,730,045.91 (+$3.99 shipping). ...

At first I thought it was a joke – a graduate student with too much time on their hands. But there were TWO new copies for sale, each offered for well over a million dollars. And the two sellers seemed not only legit, but fairly big time (over 8,000 and 125,000 ratings in the last year respectively). The prices looked random – suggesting they were set by a computer. But how did they get so out of whack?

Amazingly, when I reloaded the page the next day, both prices had gone UP! Each was now nearly $2.8 million. ...

On the day we discovered the million dollar prices, the copy offered by bordeebook was 1.270589 times the price of the copy offered by profnath. And now the bordeebook copy was 1.270589 times profnath again. So clearly at least one of the sellers was setting their price algorithmically in response to changes in the other’s price. ...

Once a day profnath set their price to be 0.9983 times bordeebook’s price. The prices would remain close for several hours, until bordeebook “noticed” profnath’s change and elevated their price to 1.270589 times profnath’s higher price. The pattern continued perfectly for the next week. ...

As I amusedly watched the price rise every day, I learned that Amazon retailers are increasingly using algorithmic pricing (something Amazon itself does on a large scale), with a number of companies offering pricing algorithms/services to retailers. ...

The behavior of profnath is easy to deconstruct. They presumably have a new copy of the book, and want to make sure theirs is the lowest priced – but only by a tiny bit ($9.98 compared to $10.00). Why though would bordeebook want to make sure theirs is always more expensive? ...

My preferred explanation for bordeebook’s pricing is that they do not actually possess the book. Rather, they noticed that someone else listed a copy for sale, and so they put it up as well – relying on their better feedback record to attract buyers. But, of course, if someone actually orders the book, they have to get it – so they have to set their price significantly higher – say 1.27059 times higher – than the price they’d have to pay to get the book elsewhere. ...

But, alas, somebody ultimately noticed. The price peaked on April 18th, but on April 19th profnath’s price dropped to $106.23, and bordeebook soon followed suit to the predictable $106.23 * 1.27059 = $134.97. But Peter Lawrence can now comfortably boast that one of the biggest and most respected companies on Earth valued his great book at $23,698,655.93 (plus $3.99 shipping).
--Michael Eisen, it is NOT junk, on how algorithmic trading can lead to strange outcomes. HT: JQ

1 comment:

Roger Grossman said...

And this is how the internet bubble burst in 2002 and how the real estate bubble burst a few years ago. Just a smaller scale.