Trouble shooting -- an easy way to recognize IP reputation

Who's using PowerMTA to send Emails, knows the amazing backoff mode.
There is a setting named "backoff-reroute-to-virtual-mta". If this is set up, then PMTA reroutes the traffic from the trouble IP to the pointed IP automatically.

Assume I have a pool consisting of 4 IPs, IP1, 2, 3 and 4.
I set up a loop by using the setting "backoff-reroute-to-virtual-mta" to reduce the queues and bounces.
It means, the traffic will be rerouted from 1 to 2, 2 to 3, 3 to 4 and 4 to 1 automatically, if there are certain issues to send out the emails over original IPs.

Since these 4 IPs stay in the same pool, they must carry the same traffic theoretically.
After the setting of backoff rerouting, they will carry the same traffic, if and only if these 4 IPs have the similar (necessary condition) and healthy (sufficient condition) reputation.

Once I check the dashboard/report and I see very different total numbers of message counts.
Depends on the number of bounces (explanation s.b.), the IP has most total sent, has the best reputation and the one has least sent, has the poorest reputation.

Why I am saying, it depends on the bounce numbers?
It happens, that all of these 4 IPs have bad reputation.
All mails ran cycle, they are ended up in one IP, for example IP1, and bounced there.
For this case, IP1 has the most traffic, most bounces, probably most deliveries, but it doesn't have a good reputation either.

This is an easy way to measure IP reputation from the sender's side.
SNDS, Return Path, etc. are not needed.