# Central Bank Rate Validation

Before returning data, the returned central bank data is validated with the following checks:

* The `RateFeed` checks that **the returned central bank rate is at most as old as the \_stalenessThreshold.** Note: Even though central bank rates seldom change (on the order of a few times a year at most), oracles are still expected to update the rate to be newer than the `_stalenessThreshold`, even if they are updating to the same rates as served in the previous round. This staleness threshold is set by the `MCAG_MANAGER_ROLE`.
* Before data is accepted in a round, the `MCAGAggregator` checks that **the rate feed's answer is less than a preconfigured maximum value, and that the newly transmitted rate has not changed too drastically from the previous rate**. See the MCAGAggregator Volatility Check section for exact calculations on how this is done.


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