Looks like you're mixing mathematical metaphors...
The future service credit model UPS uses was never inflation adjusted. The terms are negotiated.
It would be highly unusual to set accrual rates that pay out far into the future on a past yearly inflation rate.
If you do the mathematical exercise (add the yearly inflation rate of each successive year to the base rate of $132), you'll see that had the accrual been pegged to inflation for the period 2008-2017 (as you apparently wish), the rate would now be at $155, not $175.
Inflation over that period averaged 1.69%.