Researchers derive urban scaling laws from the 3D geometry of a city

When complex systems double in size, many of their parts do not. Characteristically, some aspects will grow by only about 80 percent, others by about 120 percent. The astonishing uniformity of these two growth rates is known as "scaling laws." Scaling laws are observed everywhere in the world, from biology to physical systems. They also apply to cities. Yet, while a multitude of examples show their presence, reasons for their emergence are still a matter of debate.