Log Utility Interview Intuition
Log utility interview intuition for concave preferences, drawdown penalties, Kelly links, and multiplicative growth assumptions.
Advanced candidates discussing Kelly and utility.
Concave utility
Log utility is concave, meaning an extra dollar is valued less when wealth is already high than when wealth is low.
Drawdown penalty
Because log utility punishes losses heavily near zero, it discourages all-in behavior in repeated favorable games.
Concrete intuition
Doubling wealth and then halving wealth returns to the starting point. Log changes add to zero, matching multiplicative growth intuition.
Kelly connection
Kelly sizing can be derived from maximizing expected log growth under specific assumptions.
Assumptions
Log utility is a model choice, not a universal preference. State it as an assumption if using it in an interview.
Common mistakes
Candidates often present log utility as objectively correct. It is useful because of its properties, not because every decision-maker has that utility.
Practice the pattern
Use the LeetQuidity curriculum and calibration to turn this topic into a focused practice plan.