Pull systems increase performance

Posted 8 months, 3 weeks ago at 8:05 am. 2 comments

As part of my continuing series of posts on lean and kanban boards from an I/O Psychology perspective, this post focuses on pull systems. Most people who subscribe to lean ideas think pull systems (as opposed to traditional push systems) are superior for employee performance. The most often cited reasons for this are case studies of organizational success like Toyota and others. I found that when looking through a lot of this information, there were few empirical studies that focused on aspects of lean for complex jobs outside of manufacturing. One of the few (academic) articles to test an aspect of lean, specifically pull systems, was an article by Marsh and Conard (2008).

Their article looked at a pull systems in the context of “knowledge work”, which is work that is considered to be non-physical, non-repetitive, white collar, and cognitive in nature. The traditional set up for work such as this is that information on what to do is pushed down through an organizational hierarchy from management to those who are directly responsible for the work. As you can guess, the results of push systems are having a lot of work-in-process and long lead times. Push systems often require that tasks be worked on concurrently, which tends to result in slower response times and more waste. The point of a pull system is to use a kanban board to limit work-in-progress by pulling from the previous phase of your value stream when necessary. Many studies that focus on the implementation of kanban boards for industries other than manufacturing have shown that waste is reduced when work is set up to be pulled through a series of phases.

The Marsh and Conard (2008) study found that there was a significant improvement in performance time (without significant differences in performance quality) when using a pull versus a push system. The pull system was five minutes faster than the push condition, a 9% reduction in time. Though that may not sound like much in practical terms, if the results were to be replicated in the workplace the time reduction translates to 22.5 days (assuming a typical 40-hour work week). Think about all the additional things you could do if you had another 22 work days a year!

The findings for the study also suggest that those who used pull systems as opposed to push might have had higher levels of intrinsic motivation. This fits with my first post of this kind related to motivation and lean/kanban because Marsh and Conard (2008) go on to note that “leanness” could affect motivation and performance. It seems as though the use of a pull system in this study gave participants more feedback, which motivated them to continue working. Other research like Doerr et al. (1996) has also found evidence that worker using pull systems performed faster than those using push systems, so the results are not an isolated incident even though Marsh and Conard (2008) looked at these issues in a lab. The conclusion of the paper suggests that studies like this should help shift the way that work is delegated from a push to a pull system, and I certainly hope that this is the case.

It would be interesting to see what the increase in performance might translate to in terms of the bottom line. The increase in efficiency with the use of a kanban board would be well worth the low-cost of Zen, a lean project management tool.