Input Decay Posted on 1st December 201525th April 2022 by ThePD (The Project Definition) Input Decay is the loss in the physical efficiency of an asset. Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in Management and tagged business. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.