See https://www.lesswrong.com/posts/J6gktpSgYoyq5q3Au/benchmarki.... The short answer is that linear elo growth corresponds roughly linearly to linear evaluation depth, but since the game tree is exponential, linear elo growth scales with exponential compute. The main algorithmic improvements are things that let you shrink the branching factor, and as long as you can keep shrinking the branching factor, you keep getting exponential improvements. SF15 has a branching factor of roughly 1.6. Sure the exponential growth won't last for ever, but it's been surprisingly resilient for at least 30 years.