Clustering and psychological barriers: the importance of numbers

The contemporary press frequently makes mention of, and identifies significance with, specific numerical values in financial markets. This focus has been suggested to result in clustering. Furthermore, these symbolic numbers are often referred to as psychological barriers. These effects are identified as a widespread phenomenon permeating into the economic decision making and financial market environments. This article outlines various arguments and rationale from the cultural, economic, and behavioral literature why clustering and other effects such as psychological barriers may be expected in financial markets. Evidence across a variety of literatures suggests that financial market clustering derives from a variety of sources. There is evidence from a cultural and conventional basis to suggest that number preference exists and that there is a natural tendency to round that derives from the development of the modern decimal system. The literature also provides valid behavioral and economic reasons as to why these effects may occur. However, no evidence is found to support the notion that clustering or barriers in financial markets would occur as a result of a natural order or as a product of the number progression or simply from the numbers themselves. © 2001 John Wiley & Sons, Inc. Jrl Fut Mark 21:395–428, 2001