The thing about decline is that it can last for a very long time. The world is filled with post-imperial countries whose ruins remind us of the greatness they once were. But these countries still function, dysfunctionally, generation after generation. It is easy to celebrate both ascendancy and demise. More difficult, and less satisfying, to consider the trajectories enabled by various trade-off decisions.

Some of these trade-offs seem new to us; for example, that economic growth and global military supremacy may actually be at odds—at least, after a certain resource utilization threshold has been crossed.