For mutual funds, Kwanti automatically extends the history of the fund to the oldest available class of the fund. For other assets, or for cases where the fund's oldest class history is insufficient, the missing price history is filled with the prices of a similar asset or index. This operation is called a backfill.
In the above example, the selected backtest length was 20 years, however two portfolio assets had less than 20 years history:
- IEF (iShares Bond ETF) only has history back to 2002 (shown in green.) Its price history is extended with a Barclays Bond Index.
- IWM (iShares Russell 2000 ETF) only has history back to 2000. Its history is extended using with Morningstar Small Cap Index.
Backfill defaultThe application automatically selects a backfill index by looking up the biggest allocation class for the asset, or the fund category if available. For example, a mutual fund whose biggest asset allocation is mid cap will be backfilled with a mid-cap index.
Changing a backfillTo assign a different asset for backfill, click on the blue bar representing the backfill. A menu appears with a choice of indexes, stocks, ETFs and funds, as shown below:
You may select a different backfill for each asset. When done, click 'Save Changes' to update the backtest.
Double backfillThe asset you choose as a backfill may itself not have enough history to extend to the desired period length. In this case, Portfolio Lab uses a second backfill.
In the example below, GOOG has history from 2014. For backfill, GOOGL is used from 2004 to 2014 and a Morningstar Technology Index is used as a second backfill, prior to 2004.
Unlike the primary backfill, the secondary backfill can only be chosen from a restricted set of indexes.