Perhaps you've noticed that the quality and quantity or work produced by a group of individuals is very rarely related to the number of people in the group.

I sure have!

In fact, I don't think I have ever driven by a state road work area without being amazed at how many people were on the job, and how little they appeared to be getting done. This principle is far more important in the design world however, where creativity, vision, and coherence is valued at a premium.

In projects with large design teams, much of the time of each person working on the project is spent coordinating with coworkers, and making sure they are all "on the same page". Smaller groups don't have this problem, and can therefore be far more productive! And most importantly, when larger groups try to enhance their productivity by "compartmentalizing" people to solve independent tasks without imparting them with a vision of how the whole project fits together, the project nearly always suffers significantly in quality. Perfect examples of this would be Microsoft Windows or eBay, where it is easy to see how a tremendous number of highly specialized people have produced terribly clunky systems.

Much of the coolest computer work being done today, such as Unity 3D (12 people - including marketing and support), X-Plane (Masterminded by one person, with a couple friends speciliazing in graphics and data), and Safarri (by Me :), is being done by small teams - and I predict that as the power of computers increases, this will constantly become even more true.

So - without further ado, I introduce my fundamental law of efficiency:
It applies to any areas involving creativity and talent, such as software and web development, product design, building design, and authoring.

Productivity, Quality = Cumulative Talent / involved personnel

In essence, to get a better end product faster, adding more people working on it is the worst thing that could be done (especially if it is behind schedule). The more talent and focus - and less people - that are involved, the better a product will be.