An inflation protection clause in the UPS master agreement allows for "cost of living adjustment".

UPS TEAMSTERS: NO COLA FOR YOU
It’s official: UPS Teamsters will not get a Cost of Living Allowance (COLA) raise this August 1, in addition to the base wage raise of 75c. Article 33 of the UPS Master Agreement provides for inflation protection, but only if inflation exceeds 3.4%, based on the year of May 2018 to May 2019. The US Bureau of Labor Statistics has just released the May figures, and the inflation index (CPI-W) only rose 1.7%.
You may be surprised at that, because inflation has risen faster this year. In fact, the inflation index (CPI-W) has gone up 2.1% in just the last six months, and is rising.
UPS Teamsters: No COLA For You - Teamsters for a Democratic Union