Why Do We Miss Deadlines and Overrun Budgets?

Source: USA Today

We all have experienced projects that miss key deadlines and exceed budgets.  It's not a fun experience.  In retrospect, it seems obvious that we were overly optimistic in our estimates.  Yet, at the start, we thought we had been reasonable, even conservative, in our projections.  Why do we make these crucial errors?  One study offers an interesting explanation.  Bradley Staats, Katherine Milkman, and Craig Fox once published a paper titled "The Team Scaling Fallacy: Underestimating the Declining Efficiency of Larger Teams" (Organizational Behavior and Human Processes, 2012). 

Staats, Milkman, and Fox found that people tend to overestimate the benefits and underestimate the costs of increasing team size on a project.  Adding more people can enhance expertise and skills available on the project.  However, the challenges of coordination and collaboration grow as well.  By not acknowledging those costs sufficiently, many people generate overly optimistic estimates regarding budget and schedule on important projects.  

The study confirms the intuition of leaders such as Jeff Bezos at Amazon, Steve Jobs at Apple, and Brad Smith at Intuit.  Each of those leaders advocated keeping critical work teams small and nimble.   For example, the "two-pizza rule" maintained that you should be able to feed the entire team with two large pizzas (meaning the team should probably not exceed 6-7 members).