What you need to know:
This allows companies that have your address (which data brokers generally do through other sources) to perpetually have up to date information, even when you move. These data brokers can then in turn sell your addresses to other companies, including those that may sell products or services in your new neighborhood or specifically for “new movers”.
If you want to forward your mail forwarded to a new address, the USPS does not offer an option to opt out of them selling this data.
What to do:
There is a loophole that keeps data brokers from accessing your updated address when you move. When you fill out an address change form online you can indicate a temporary change that provides 6 months of mail forwarding, which can then be extended for another 6 months. That information is not included in lists sold to data brokers.
An alternative is to get a P.O box and have mail forwarded to the P.O. box instead of your residential address.
Although, even if your address is not shared directly from USPS to data brokers, these brokers still have many other ways to collect this information.