Abstract
This paper provides a model of rational OTC dealers trading at a fix. It predicts four forms of misconduct that have been documented for fixes in FX, silver, and gold: front-running, a form of predatory trading; banging-the-close, a form of trade-based manipulation; information sharing; and collusion. This misconduct generates heretofore puzzling features of fix-price dynamics: high volatility before the fix, partial retracements thereafter, and an accelerating price trend as the fix approaches. Additional support for the model emerges from statistical tests for trend acceleration around FX fixes.