I'm a little confused by the question:
- absolute pressure - I'm running Sumitomo T4s with 51 psi front and 49 psi rear.
- relative pressure - My Sumitomo T4s are rated at maximum sidewall pressure of 51 psi so my relative pressure is 0 psi front and -2 psi rear.
- OEM pressure - Toyota recommends 32 psi for OEM tires that came with my 2003 Prius so my replacement Sumitomo T4s are running +19 psi front and +17 psi rear.
Let me suggest that one or more polls might be a more efficient way to collect the tire pressure spread. Of all metrics, I would be more interested in the 'relative pressure' compared to the maximum sidewall pressure value. But given non-USA folks use standard units, a relative percentage might be more useful and easier to deal with.
It is a good question.
Bob Wilson