Users can see how the witnesses answered this question on the PeakD witness page.

https://peakd.com/me/witnesses

It appears that the witnesses can simply type in a number.

The number of witnesses that vote for exactly 20% is interesting. This implies that there are whales who want 20%. My guess is that witnesses have to vote 20% to get whale votes.

As for the answer to the question: To maintain a balance, the interest on HBD should be significantly lower than that paid on HIVE.

Since interest is not inherently important to HBD, I would vote 0%. But I suspect that the public at large would prefer something like 10%.

!WINEX