A mystery novel, a history book, and a fantasy epic may have little in common in plot or style. But count the words inside them and a strange regularity appears: many new words show up early, then fewer and fewer as the author reuses what has already been introduced. That pattern, known as Heaps’ law, turns out not to belong to books alone. A new study in PNAS, led by SFI and MIT researchers, finds that the same rule also describes how complex systems grow, from living cells and corporations to universities and government agencies. As these systems get bigger, they add new functions more and more slowly. While systems vary in how much they invest in creating new functions, once those exist, their subsequent growth slows, following a remarkably universal pattern known as sublinear growth. santafe.edu/news-center/news…

A significant body of research has investigated why, as city populations grow, so do violent crime, contagious diseases — and per-capita GDP. A new paper now finds that cities with strong interconnectivity show a marked economic benefit, even beyond normal scaling. santafe.edu/news-center/news…

PhD student opening at MIT Sloan System Dynamics! Seeking aspiring social system modelers (esp. dynamical system), wanting to take the social sciences seriously. Generous fellowship funding, free to work with me or any of our talented SD faculty. mitsloan.mit.edu/programs/ph…