Context-Sensitive Choice and the Spectrum of Aggregate Dependence: Salience, Costly Attention, and Concentration Collapse

When many people pay attention to the same things, the risks they jointly create pile onto a single axis, and the market starts to move as one. This paper turns that idea into theorems. What people's choices reveal is only the undirected part of this shared dependence; the direction of attention, who draws whose eye, is invisible to the data, so the paper refuses to claim it rather than smuggling it in by assumption. As shared attention grows, dependence concentrates, and the passage into concentration is a clean tipping point with no jump and no hysteresis. Below a measurement floor a single mode of attention cannot be told from noise, so the correct report is to abstain. The paper draws the boundary between individual attention and systemic concentration, and says which parts of it data can certify.