Can Multi-tasking Result in More than 60% Longer Project Time?

You want to be perceived as a good innovation project member, to be appreciated for your achievements – and just to safeguard that notion some of what you do leads to a success in time – you do multiple projects in parallel. But is this really efficient and effective? Check out Bengt Järrehult’s somewhat mathematical look at multi-tasking, where the exercise of putting numbers in leads to a result that may surprise you.

Two projects, A and B, can run in two different ways, both demanding ten weeks of full-time work. It seems to be virtually irrelevant whether we run one week with A and then one week with B, etc. (multi-tasking) or if we complete A before starting with B (single-tasking). In both cases we are ready after 20 weeks (see fig 1). But if we calculate the average time per project, using multi-tasking we get 19.5 weeks per project because A is ready after 19 weeks and B after 20 weeks, i.e. average 19.5 weeks. If we run single-tasking, A is ready to be launched to earn money after 10 weeks (see the red flags) while B is ready for launch after 20 weeks, both calculated from time = 0. The Average time per project is now only 15 weeks (as (10+20)/2 = 15). Therefore multi-tasking decreases the efficiency 30%! (as (19.5 -15)/15 =0.30). Do you agree?

Figure 1: Running two projects each demanding 10 weeks full time work.

Click to enlarge

If we make a similar check with three projects (D, E & F) each demanding six weeks full-time work (Fig 2), we see that multi-tasking results in 41% longer average project time than single-tasking!

Single-tasking = (6+12+18)/3 = 12 weeks

Multitasking =(16+17+18)/3 = 17 weeks

Difference (17-12)/12 = 41%

Figure 2: Running 3 projects each demanding 6 weeks full time work.

Click to enlarge

In reality it’s even worse because we have “shifting time” between projects. It usually takes time to re-focus your energy to the demands of project B after you have worked an entire week with project A.  Let’s say that after one day you are fully re-programmed (Fig 3, right) and up and running at 100% activity level. This means a 20% loss in time due to the shifting time if you have the interval of five days (one working week) for each project at a time.

Figure 3: Effect of shifting time on projects after one shift.

Click to enlarge

Transferred to the situation first mentioned with the projects A and B, the full effect (Fig 4) is that you have nineteen shifts in the multi-tasking approach but only one shift if you’re single-tasking. Including the shifting time, this leads to time lost for multi-tasking compared to single-tasking increasing from the above mentioned 30% to remarkably high 52%!

Figure 4: Full effect of shifting time on projects A and B.

Click to enlarge

Used in a realistic situation (e.g. four projects at twenty six weeks each, run in half-week intervals but only a half-day time loss each shift) this means multi-tasking results in 66 % longer average project time! As an excuse speaking for multi-tasking you may state it is advantageous to have several projects to alternate with, because when there is a delay in one project due to “external circumstances” you can switch to another project instead. This may be true, but if you run them one-at-a-time, you would not accept any delays. Instead, you would turn every stone to fix these external circumstances, so I don’t buy that excuse. Single-tasking indeed means increased focus and dedication that favor both the quality and quantity of delivery.

You also have other delaying effects of multi-tasking; for example you can’t have project team meetings when needed. You often have to delay meetings, because your team members are occupied in other project meetings or activities. (You recognize this, don’t you?) So the message is …Reduce the number of projects you participate in so you can practice single-tasking.  Finish old activities before starting new. Reduce lead times accordingly. Doing this you will deliver innovation projects more efficient and more effectively. Less is undoubtedly more!

By Bengt Järrehult

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About the author


Bengt Järrehult is Fellow Scientist Innovation at SCA, a global hygiene products and paper company. He is also adjunct professor and visiting professor resp. at 2 departments of Lund University in Sweden. He is an avid reader of and presenter on the topics of innovation, especially on breakthrough innovation and the psychological hurdles that exist to achieve this, hurdles that we may or may not be aware of. He is of the opinion that most companies more or less know what to do to become more innovative. What they don’t know is what really hinders them from doing these measures…

  • http://profiles.google.com/marcuslinder Marcus Linder

    Beautiful illustrations Bengt! :-)

    I believe you might be underestimating how often some of us have to wait on external resources and how difficult this can be to accurately predict (and consequently plan around). And perhaps also the tendency for some good ideas to need a certain amount of calendar time to develop properly. The kind of insights I tend to get while biking home from work or digging a trench for a new hedge.

    But that being said, I absolutely love your pedagogical description of the inherent losses of multitasking!

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  • Rebecca Tversky

    Thanks for the detailed breakdown! I like your ideas and see much of the value of focusing on tasks and projects. It is good to focus on one task at a time, using natural breaks to shift to the next project or client (lunch, meetings, breaks, etc.). As Marcus Linder said, there can be a lot of downtime for individuals waiting for information, decisions, or other work to be in place before they can start. We find that carrying on multiple projects at different stages is effective, so that when a specific type of work must be done, it gets the full attention of the people involved. We gather the materials and information needed for a task than gather the team to focus on completing that step until we’ve generated what’s needed for the next one, etc. The number of projects possible varies with the team and client. It’s an ongoing experiment in improvement.

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