The Mythical 50% Resource

Scheduling | By Dave Nielsen | Read time minutes

Red blocks with the percent sign on a white background

Most managers of software development projects have had an encounter with a resource who is committed to their project some percentage of the time. The most common approach to splitting a resource between two tasks is to assign them 50% to both, although other percentages can occur. It's even been known to have a resource assigned to more than two tasks 50% of their time! Sharing a resource with another project or functional manager would not be a problem in a perfect world, but ours is never a perfect world and sharing a resource with another manager can present some challenges for the project manager. Here are some tips and tricks you can use to make the best of the situation.

When Sharing a Resource Won't Work

Never plan to employ a resource whose time is more than 100% accounted for. Your grade school math isn't wrong; there are still only two halves in a whole! It may seem like I'm stating the obvious here, but this situation does happen and the math gets explained away with excuses such as "Joe works a lot of overtime, so you can expect him to spend 20 hours a week on your project", or "Jane is very productive, she can easily deliver 50% more than any of the other programmers." Don't fall for it! Joe may work 20 hours of overtime one or two weeks, or even one or two months, but you can't expect him to keep up that pace throughout your project. Jane may be every bit as good as they say, but as the effort estimate for the work she will be performing is likely to come from her, you would have to factor in a 50% buffer to have a chance of meeting deadlines and that 50% buffer is going to be difficult to explain to your stakeholders. The chances of you getting one third of her time are also pretty remote.

Beware of situations where your partner manager is not in control of the amount of time the resource spends on their work. Help desk work is a perfect example. A developer who is scheduled to spend 50% of their time answering customer calls and resolving issues won't be able to guarantee they will only spend four hours of the day on that activity because they can't simply drop an issue which they are in the middle of resolving for a customer.

You have three choices when faced with a sharing arrangement that won't work: Negotiate a split to 100% of that resource's time, delay engaging the resource until you can get 100% of their time, or engage a resource to replace the one to be split.

When Sharing a Resource Will Work

There are times when a critical resource must be shared across multiple projects or operational activities. For example, when you need a resource for a task on the critical path and no other resource will do, you will have to compromise. Even when the task isn't on the critical path, postponing it may put it on the critical path before you identified an alternative solution.

Sharing a resource in an organisation which has experience with resource sharing, and with other managers who are experienced in sharing them, gives you more chance of success, but even if you're sharing a resource in an organisation unused to such arrangements and with other managers without experience in this area, there are tips and tricks you can use to improve your chances of success.

The key to successful resource sharing is teamwork between the sharing managers. To work successfully as a team, the managers must realise that the objectives of the projects or operational activities must be considered equally. If this weren't the case, the resource wouldn't be shared; they would go to the highest priority project or operational task. Teamwork here means that the sharing arrangement is planned between collaborating managers and a successful plan is one that supports both sets of objectives. Teamwork will also mean that the manager, or managers, you share resources with are now stakeholders in your project and should be treated accordingly in terms of project communications and any changes or risks that impact the shared resources.

Time Share

Time sharing is common practice now when customers share a vacation property and the same things that make this workable for vacation properties can facilitate sharing a resource. The "Time Share" approach plans the resource 100% on the activities of the first project. Once those activities have been completed the resource moves to the second project 100% of their time. This can be repeated as many times as necessary. Use common sense when determining the duration of the resource's stay on either project; the longer the resource spends on one task the more efficiently they will work. One day should be the absolute minimum block of time, with one week being the preferred minimum.

Compare project plans with the manager you plan to share the resource with to determine when the resource is needed on both projects. If the times at which you both require this resource clash, examine both plans to determine if activities can be juggled so that the resources activities can be sequenced in such a way that the resources time can be planned from start to end 100% on the first project, 100% on the second project, etc. until the resource can be released from both projects. Be flexible when planning this with your partner manager; you will both have to make some sacrifices in order to make this arrangement work. Working with an operational manager to achieve a time sharing arrangement will work the same way, but the operational manager may have more constraints which prevent them from re-scheduling activities.

Once you've reached an agreement on time sharing, update your project plan accordingly. MS Project provides calendars for individual resources. These calendars allow you to set aside time for the resource for individual activities such as training or vacations. Define the times the resource will be working on the partner project or operational activity as "unavailable." This will prevent you from accidentally scheduling your shared resource during a time when they are working on the other project. Remember that any schedule changes that involve the shared resource will have to be discussed with your partner manager. Acquisition and release dates become contracts between you and the other manager. You must honour your release date and expect the other manager to do likewise. Avoid any schedule slippages that impact the start or finish date of your shared resource's tasks. Slippages that can't be avoided need to be discussed with your partner manager. Your partner manager may be able to give you some extra time at end date, or utilise the resource after their start date if you give them enough notice. Remember that this arrangement works both ways so be prepared to accommodate your partner PM should the need arise.

The 50% Solution

There are situations where it is impossible to sequence the work of a shared resource, for example when a resource is responsible for ongoing support work which requires a few hours daily. The only possible solution in this case is to divide the resources time between your project and your partner manager's work.

The 50/50 split (or some other configuration) depends on a good working relationship with your partner manager and that manager's ability to control the resources time when they are working on their project or operational tasks. Define the terms of the sharing agreement with your partner. An arrangement which has the resource working on your project in the morning and the other project in the afternoon is the arrangement with the most chance of success so try to arrange the split so that the transfer happens at some natural break during the day - lunch break, or coffee break.

Terms of sharing should be formally documented, an email or memo will do, but the document needs to capture the details of the arrangement, including start and stop dates, percentage split, how the resource's time is to be scheduled, and when the resource should be working on your project and when they should be working for the partner manager. This is your contract for sharing the resource. Hold your partner manager (and the resource) to the terms of this agreement and make sure you honour all your obligations.


There are some situations where resource sharing won't work and these must be worked around. If all else fails, escalate the issue to your sponsor explaining your need for the resource and why the sharing arrangement won't work for your project. In those situations where sharing can work, the easiest arrangement is the sequencing of the resource's activities between the two projects and when that can't be done, define the sharing arrangement in a formal document. Remember that there are two criteria for a workable sharing arrangement: the feasibility of the arrangement and the agreement between the two managers. Lastly, don't forget that when you share a resource with another manager that manager becomes a stakeholder in your project and you need to keep them in the loop.

The tips and tricks described in this article are intended to help the project manager using the best practices promoted by the PMI. Project managers who are certified have already implemented those best practices. If you haven't been certified as a PMP (Project Management Professional) by the PMI and would like to learn more about certification, visit the three O Project Solutions website at: three O Project Solutions also offers a downloadable software based training tool that has prepared project managers around the world to pass their certification exams.


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