Where the data comes from
Sources, update frequency, currency and what the prices include.
Every number on Backtes.to starts life as a price series. Understanding where that series comes from (and what it contains) is the fastest way to read a backtest correctly, and to understand why two different tools can produce slightly different results for the same portfolio.
What the prices include
Historical series for ETFs, bonds and stocks are denominated in euro. If a product trades in another currency, conversion uses the historical exchange rate for the period: currency risk is therefore already baked into the result you see, exactly as it would have been in your own brokerage account.
| Item | Included in the simulation |
|---|---|
| TER (ongoing product cost) | Yes, subtracted from performance |
| Dividends and coupons | No |
| Currency risk | Yes, via conversion to euro at historical rates |
| Trading commissions | Only if you set them in the settings |
| Taxation | If you set it yourself |
Excluding dividends is the single most important thing to keep in mind. For an accumulating product it makes no difference, because income is already reflected in the price. For a distributing product, the result you see is net of the coupons paid out: the real return on your position, reinvesting those coupons, would have been higher.
How often the data updates
Data is refreshed every week. The backtester works on a monthly basis and uses end-of-month values, so a few days' lag on the most recent data point does not change the outcome of an analysis, it only affects how recent the last complete month is.
Why data starts before the product existed
You will often see an ETF launched in 2019 with a series going back to 1990. That is not a bug: the history has been reconstructed, by applying the real product's costs and rules to the underlying index.
Reconstruction answers a question that real data cannot: how would this strategy have behaved in 2000, or in 2008, markets most modern ETFs never lived through. A backtest limited to the last six years describes almost nothing but rising markets.
Every reconstructed product is labelled as such, and the method is documented per category:
- Reconstructed equity ETFs
- Reconstructed bond ETFs
- Reconstructed commodity ETFs
- Full catalogue of reconstructed products
The euro before 1999
The euro has only existed since 1999, but many series start well before that. For that period prices are converted using the irrevocable conversion rates and the preceding national currencies, producing one continuous, comparable series.
The method is explained in full in The euro before 1999.
A product is missing
If an ETF, bond or stock does not appear in search, it almost always means it is not part of the current data package. You can report it through the in-app form: reports help us work out which data is worth buying, but they do not guarantee that any individual product will be added.
There is an immediate alternative, though: if you have the historical series yourself, you can upload it as a custom product from Portfolios → Your ETFs/bonds/stocks → Your custom ETFs/bonds/stocks, in CSV or Excel format. It then works in backtests like any other product.