A Portfolio's Historical Market Value Chart

The market value chart of the portfolio is a chart of the closing value of your portfolio over time. Movement in the chart is due to the price movement of your holdings as well as any cash flows into/out of your portfolio.

You can view a chart of the historical market values of your portfolio over time. To do this, click on the Total line of your Portfolio.

Note that the Market Value chart is only available for the end-of-day time ranges. That is, for ranges 4W and longer. Intraday charts (1D and 5D) are not available for the Market Value chart.

There are 2 ways the chart can be calculated. Which way is used depends on the "Calculate the Portfolio's value chart using the strict method." option on the portfolio's "Portfolio Properties" screen:

By default, the daily values used in the chart are calculated by taking the current portfolio and working backwards in time. For each previous day, the value of the portfolio at close is calculated using historical quotes, then any transactions that occurred on that day are reversed.

The right-most point in the chart (i.e. today's date) is calculated from the values in the Prices view. This value will change throughout the trading day due to new, live quotes coming in. Note, however, that the value won't update automatically, but will be updated when switching back to this chart from another chart.

With the “strict” method option selected, the daily values used in the chart are calculated by "playing forward" the transactions in this portfolio to build a virtual portfolio from scratch. For each day, the transactions that occurred on that day are applied to the portfolio and then the value of the portfolio at close is calculated using the historical prices of the individual holdings in the portfolio on that day.

The “strict” method is technically more accurate, but can result in large discrepancies if there are any missing historical quotes for stocks or currencies used in the daily valuation. The default method can also be affected by missing historical quotes, but does a better job of remaining more in-line with the current valuation of the portfolio.

For both methods, it is important that your portfolio have a complete and correct transaction history. As the chart is built directly from the transactions, any discrepancies in the transactions will affect the curve of the chart. If there is a discrepancy between the portfolio represented in the Prices view and the transactions, this can also affect the chart calculation, and in this case rebuilding the Prices view from the transactions is recommended.

What Are the Spikes in the Chart?

Spikes, either up or down, can be due to several things.

Cash flows into/out of the portfolio. As cash deposits or withdrawals increase or decrease the total value of your portfolio, they cause spikes in the chart if the amount of the change is significant enough. Dividends typically won't be visible in the overall total value of the portfolio, but depositing $10k into a portfolio that has only $50k in it will make a visible spike up.
Incorrect split transaction. If a split occurred in one of your holdings, but the you have not entered a split transaction for it or the split transaction is incorrectly entered (such as an incorrect date), the valuation of that holding will be incorrect with respect to the historical pricing (which is automatically adjusted by the provider) and thus the portfolio's total valuation will be off. This can cause either a spike up or down depending on the type of split. If your transaction is entered but is a few days off from the actual date on which the split affected the historical prices, there may be a temporary spike up or down in the chart.
Securities without historical quotes available. If you have securities for which historical pricing is not able to be downloaded, such as for non-quoted items, this can cause spikes and incorrect valuations to be calculated for your portfolio. If you have non-quoted items in your portfolio, you may want to consider importing historical price data for those ticker symbols to make the valuation calculation of that holding more realistic.

Why Don't the Chart Values Match the Total in the Prices View?

The last value in the market value chart should match the current value in the Total line of your portfolio's Prices view. If this is not the case, here are a few things to consider:

The market value chart is built from the transactions of your portfolio as described in the section above, "How is this chart calculated?" If the Prices view of your portfolio is out-of-sync with the Transactions, it will lead to different values in the market value chart than in the Prices view. You can rebuild your Prices view from the transactions, which will get them and the market value chart in sync.
If the differences are small, it's possible that the data in the Prices view has been updated more recently than the last value in the market value chart. You can try viewing a different security in the chart, and then switch back to the market value chart to get it to re-calculate and take the current value from the Prices view.
Many of the issues that cause spikes in the chart (see section above) can also cause differences between what you see in the Prices view's Total line vs what you see in the market value chart.

Can I Export the Values from the Chart?

Yes, the values from the chart can be exported to a CSV file. First, load the market values chart by selecting the Total line. Then use the chart menu Gears -> Advanced -> Export to CSV...