Had a question reguarding my portfolio return calculation. The numbers and returns percentage are taken staight out my eTrade account performance page. Here is the messeges regarding the eTrade Time-weighted Performance Method.

Investment results are historical. Past Performance is not an indicator of future results. The investment performance figures presented on the E*TRADE FINANCIAL Web site are an estimate of aggregate security performance and are calculated nightly using the time-weighted performance method. The performance figures will provide the user with a compounded percentage rate of return for an account (stocks, bonds, options, mutual funds, money market, etc.) Investment performance is calculated net of commission expense. Because the time-weighted performance method is used, any customer-initiated deposits made to the account should not increase account performance, and any customer-initiated withdrawals made from the account should not decrease account performance. The performance information should not be considered tax advice and should not be used for tax purposes. The results shown do not include the effects of gains or losses that may have occurred in your portfolio outside the date range you selected.

Time-weighted Performance Method - A method of calculating the compound growth of a portfolio that eliminates the distorting effects of money flowing into and out of the portfolio. With the method, the effect of cash flows is eliminated by assuring a single investment at the beginning of a period and calculating the average annual total return to the end of the period.