The Rate of Return (ROR) on our statements uses the Modified Dietz Method of ROR calculation, which is AIMR (Association for Investment Management and Research) compliant. The Modified Dietz method provides an estimate of a true Time-Weighted Rate of Return by weighing each cash flow by the amount of time it has been held in the account. For a detailed explanation and a numerical example of this calculation methodology, please review the Rate of Return FAQ on the Forms page of your Participant account. The rate of return displayed on a statement is a personalized figure, which takes into consideration your individual account activity and cash flows. However, in the absence of all of the necessary inputs (a beginning balance as well as an ending balance for each investment during a specific period), or if the investment has had a transfer transaction to another investment during a specific period, the time-weighted rate of return cannot be calculated. In these cases, we suggest that you look at the Gain/Loss column on statements where their performance is expressed in dollar terms which will allow you to extrapolate a traditional (non-time-weighted) rate of return for the portfolio for a specific period. Statements can be generated for any period of time on the website. The gain & loss column is always populated regardless of account activity or beginning/ending balances, and data is calculated in daily increments.