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Last tested: Jan 21, 2019
No they cannot: As mentioned here https://docs.looker.com/reference/field-reference/measure-type-reference#percent_of_total
percent_of_total measures are calculated after data is returned from your database. This means that you should not reference a
percent_of_total measure within another measure; since they might be calculated at different times, you may not get accurate results. It also means that
percent_of_total measures cannot be filtered on.
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