We conducted a choice experiment to investigate whether retirement savers follow simple portfolio theory when choosing investments. We modeled experimental survey data on 693 participants using a scale-adjusted version of the latent class choice model. Results show that underlying variability in response was explained by age and “risk profile” score and that preferences varied with income and age. Younger individuals were conventionally risk averse, but older, higher-income individuals may react positively to both higher returns and increasing risk, when risk is presented as widening ranges of possible outcomes. Respondents tended to choose among a few similar investment options.