starter question

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When a recipe calls for a 50-50 starter is that by volume or weight?

thanks from Iowa

In baker's percent, flour is always 100%.  So...not clear what 50 -50 is meant to be.  I'd assume it means, in baker's percent terms 100% flour and 100% water - or, equal weights of both.  I doubt the formula is meant to be one of volumes.

Larry