One of the things that is hard to appreciate in complex systems is path-dependence — the fact that most systems have memory. What we see today is a consequence of what came before. This is a very simple thing to say but even when we know it, we forget it and we don’t really think about its ramifications. If we want to change things, it helps to be upstream of the change. The earliest decisions are often the most significant ones. The things we have to react to are often most determinative of ho...