Expected First Pass Yield for selective soldering

We are experiencing widely varying First Pass Yields for selective soldering. Some boards are near 100% while others are less than 50% depending on the pitch and general complexity of the board.

Question: If you are running 100 boards through your selective soldering machine and each board had approximately 300 joints (mostly connectors), roughly how many of that 100 piece run do you think would come out 100% defect free, without the need for touchup/rework based on your past experience? In other words, what is a real life First Pass Yield, not Defects Per Million Opportunities for the average selectively soldered board? Thanks!

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