JEFFERSON CITY— To reflect estimated changes in the wholesale cost of natural gas as well as a change in the company’s Actual Cost Adjustment (ACA) factor, Liberty Utilities' customers will see natural gas rates decrease under a filing that takes effect on Dec. 3. The ACA factor is a mechanism which tracks any over-collection or under-collection of actual natural gas costs over a 12 month period. The net over- or under-collected balances are subsequently either refunded or collected the next year.