Thursday, September 29, 2011

Left-Digit Bias

Chapter 22 of my favorite textbook discusses various ways in which individual decisionmaking deviates from standard notions of rationality.  Here is a new one to me (from the NBER Digest):
In Heuristic Thinking and Limited Attention in the Car Market (NBER Working Paper No. 17030), authors Nicola Lacetera, Devin Pope, and Justin Sydnor focus on the used car market and ask whether it is affected by consumers exhibiting a heuristic, or short cut, known as left-digit bias: the tendency to focus on the left-most digit of a number while partially ignoring other digits.
Using data that come from wholesale auctions encompassing more than 22 million used car transactions, the authors document significant price drops at each 10,000-mile threshold from 10,000 to 100,000 miles, ranging from about $150 to $200. For example, cars with odometer values between 79,900 and 79,999 miles, on average, are sold for approximately $210 more than cars with odometer values between 80,000 and 80,100 miles, but for only $10 less than cars with odometer readings between 79,800 and 79,899.