How did fixing the deadline, not the to-do list, triple productivity?

Adopting timeboxing more than tripled developer productivity at DuPont in the 1980s. The principle is simple: instead of fixing the to-do list and letting the deadline slip, you fix the deadline and let the to-do list shrink to fit. Timeboxing is the allocation of a maximum unit of time to an activity, called a timebox, within which a planned activity takes place. A timeboxed schedule is divided into separate time periods, each with its own deliverables, deadline, and budget.

Project management generally recognizes three constraints: time, cost, and scope, and changing one usually affects the others. Without timeboxing, projects typically work to a fixed scope: when it becomes clear some deliverables can't be finished on schedule, either the deadline gets extended or more people get added to finish the same fixed scope in the same time, and often both happen, resulting in delays, higher costs, and often lower quality. With timeboxing, the logic flips: the deadline is fixed, which means the scope has to shrink instead, so the team has to finish the most important deliverables first.

The same idea scales down to a single person's afternoon. Timeboxing can be used for personal tasks on a reduced scale of time, like thirty minutes, and a reduced scale of deliverables, like a household chore instead of a project milestone, where it's often called timeblocking. Personal timeboxing is said to act as a life hack that helps curb perfectionist tendencies, by setting a firm time limit and not overcommitting to a task, which can also sharpen creativity and focus by creating a sense of urgency. The Pomodoro Technique applies the same logic in miniature, built on 25-minute timeboxes of focused concentration separated by breaks that let the mind recover.