Labor density is not a measurement that is thrown around very often, at least explicitly. Conceptually however, it must be resident somewhere in the lean thinker's headset. Hey, it was important enough for Taiichi Ohno to discuss!
Labor density is a measure of value-add intensity relative to total worker motion. The measurement provides insight into the extent that a worker’s motion transforms the materials or information (or in the instance of health care – helps the health or comfort of the patient) into something that is valued by the customer. Ideally, the labor density should be 100%.
The waste of motion, both physical (searching, twisting, bending, etc.,) and virtual (searching within a database, moving from computer screen to screen), consumes time and resources, but does not add value. While total work content is not necessarily limited to only motion, labor density can help highlight wasted motion whether it is an act of omission (motion that substitutes for real value-added work, like “apparent” work instead of properly securing the required three fasteners) or plain old, waste of motion.
- Labor density = work / motion
- Example: If value-added work is 32” and total worker motion is 40” per cycle: 80% = 32” / 40”
Admittedly, the labor density measurement is not very sexy at all, but it should challenge us to more rigorously observe, identify and eliminate waste!
Related post: Musings About FIFO Lane Sizing “Math”