Brake Pads

Does anybody know why my brake pads are wearing out not equally on both sides of the rotor? It is on rear wheels on both sides, driver and passenger. Last year I did change calipers - I tought they are locked, but now, just 11 months later it's this same. Inside pads are like new, outside are worn out to the metal.
Andrew

Caliper not sliding on the mount?

Caliper not sliding on the mount?

This is what I tought - calipers or their mounts are defective, but now I have new calipers. I think it is not related to calipers since I did exchange them and on both sides of the car pads are wore out in this same way.

Andrew

I have the same problem on my 92 Lumina Sedan.
The rear pads wear down very quickly and I've replaced them about every 18 months. I've heard that this is common on the Lumina's. I've checked mine and they seem to slide easily back and forth.