<prompt> Human: I was researching whether to move my Roth IRA to a traditional, and I stumbled on this note here:According to the Employee Benefit Research Institute, traditional IRAs grew at only half the rate of the better-performing Roth IRAs in 2014.Is this true? What could possibly cause that?  <response>: Roth IRA investors are more likely to be in lower tax brackets, therefore younger, therefore invested more aggressively.TL;DR Omitted variable bias 