Why good task prioritization can mean doing lower priority tasks first

At the I company work for, tasks are assigned on a quarterly basis, and people are frequently assigned more tasks than they are expected to accomplish in that quarter. Tasks are assigned priorities, and the guidance given is to try to accomplish the higher priority tasks. And if the lower priority tasks are not completed, that is expected and okay.

Sometimes, this can lead to the misconception that the best strategy is try to finish the higher priority tasks before working on the lower priority tasks. However what is not being considered is how tasks often have dependencies on other tasks. And delaying the completion of a task, can delay the completion of many other tasks. For simplicity that let’s assume that tasks have deadlines such that completing the task before the deadline prevents a delay in dependent tasks.

Taking deadlines into account, it can often be better to work on tasks with earlier deadlines even if that means working on a lower priority task first. For example, let’s pretend we have 2 tasks that both take 1 week to accomplish. The lower priority task is due next week and the higher priority task is due in 2 weeks. The optimal scheduling strategy is to accomplish the lower priority task first, and then work on the higher priority task.

A heuristic to arrive at the optimal task schedule, is to estimate how much time you need to finish all your high priority tasks before their deadline, and use that as the date when you will start working on all the high priority tasks. Before that date, work on the lower priority tasks that have earlier deadlines.

In practice there is often a huge backlog of lower priority tasks that have yet to be begun, and in our formulation this implies that they have very early deadlines because taking the first step unblocks a whole chain of subsequent tasks. And the high priority tasks have a deadline that is the end of the quarter because that is what was agreed upon. Therefore in practice, the optimal task scheduling often looks like doing a bunch of lower priority tasks before tackling the higher priority tasks.

This task scheduling strategy has the drawback of looking bad because management may be wondering why you keep delaying the start of high priority tasks and spending so much on low priority tasks. So adjustments in this strategy need to be made to optimize in the full complexity of the problem that life presents to us. That is left as an exercise to the reader.