A castle builder decided to get really analytical.

“Statistics show,” he said, “that 95% of the part of the castle defenders use in combat is the top 5 feet.  But the lower parts of the castle are the great majority of the time and the expense of building.”

He mused.

“Think of how much more effective I can build if I skip straight to the only useful part instead of being blinkered by hidebound traditionalism.  I will call it The Castle in the Air ™!”

Moral: Numbers are no substitute for wisdom.