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For every three projects in parallel,

you can do five in sequence.

 

Why?

The reason is quite simple: each time anyone doing technical work is interrupted, they lose 15-20 minutes to get back into their train of thought. This applies to BA’s testers, architects, developers etc. What is happening in their heads, is the same as what is known as context switch in a computer.

 

There have been standards describing the reduced utilisation as a result of doing multiple projects in parallel (late 1990’s) but we cannot find the references anymore. The gist is that if you do 2 projects you lose 20% utilisation, 3 projects you lose 30%, 4 projects more than 40%. So if you work on 2 projects at the same time, then 1 day a week is lost on switching your attention!

 

We have built pipe-line / demand planning spread sheets where we have taken these rules into account and have found a stunning correlation with reality on the work floor. The numbers are very much as described for projects of several months - the reduced utilisation is a little lower if your “projects” are short jobs in a maintenance pipeline setting.

 

And here is a simplistic proof of why you can do almost five projects in sequence in the same time span as doing three in parallel.

 

 

Others have found the same via different means. For example, in the early 2000’s the Productivity Institute had on their web-site a dynamic picture showing a simulation on how project end-dates slip if you do projects in parallel. In this picture they show how slippage occurs due to not being available at the right time. Unfortunately it is no longer available on their web-site so we have re-published it here.

 

 

(Reload the page (press F5) to restart this image)

 

The above is not ours and we refer you to their web-site for any further enquiries.

pdinstitute.com/AllFramePages/FP_PDI_Home.html

 

So the lesson is – by asking internal or external customers to wait, they get their stuff faster and cheaper (they don’t now need to pay for the context switch time loss), and you can be more productive!

 

The other benefits are that you have a much better chance to deliver on time as promised, and to the customer it doesn’t appear that things are going slow (when you work for them they have all your attention)

 

 

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