Inference compute scaling might imply we first get fewer, smarter AIs.

Prior estimates imply that the compute used to train a future frontier model could also be used to run tens or hundreds of millions of human equivalents per year at the first time when AIs are capable enough to dominate top human experts at cognitive tasks^[1] (examples here from Holden Karnofsky, here from Tom Davidson, and here from Lukas Finnveden). I think inference time compute scaling (if it worked) might invalidate this picture and might imply that you get far smaller numbers of human equivalents when you first get performance that dominates top human experts, at least in short timelines where compute scarcity might be important. Additionally, this implies that at the point when you have abundant AI labor which is capable enough to obsolete top human experts, you might also have access to substantially superhuman (but scarce) AI labor (and this could pose additional risks).

The point I make here might be obvious to many, but I thought it was worth making as I haven't seen this update from inference time compute widely discussed in public.^[2]

However, note that if inference compute allows for trading off between quantity of tasks completed and the difficulty of tasks that can be completed (or the quality of completion), then depending on the shape of the inference compute returns curve, at the point when we can run some AIs as capable as top human experts, it might be worse to run many (or any) AIs at this level of capability rather than using less inference compute per task and completing more tasks (or completing tasks serially faster).

Further, efficiency might improve quickly such that we don't have a long regime with only a small number of human equivalents. I do a BOTEC on this below.

I'll do a specific low-effort BOTEC to illustrate my core point that you might get far smaller quantities of top human expert-level performance at first. Suppose that we first get AIs that are ~10x human cost (putting aside inflation in compute prices due to AI demand) and as capable as top human experts at this price point (at tasks like automating R&D). If this is in ~3 years, then maybe you'll have $15 million/hour worth of compute. Supposing $300/hour human cost, then we get ($15 million/hour) / ($300/hour) / (10 times human cost per compute dollar) * (4 AI hours / human work hours) = 20k human equivalents. This is a much smaller number than prior estimates.

The estimate of $15 million/hour worth of compute comes from: OpenAI spent ~$5 billion on compute this year, so $5 billion / (24*365) = $570k/hour; spend increases by ~3x per year, so $570k/hour * 3³ = $15 million.

The estimate for 3x per year comes from: total compute is increasing by 4-5x per year, but some is hardware improvement and some is increased spending. Hardware improvement is perhaps ~1.5x per year and 4.5/1.5 = 3. This at least roughly matches this estimate from Epoch which estimates 2.4x additional spend (on just training) per year. Also, note that Epoch estimates 4-5x compute per year here and 1.3x hardware FLOP/dollar here, which naively implies around 3.4x, but this seems maybe too high given the prior number.

Earlier, I noted that efficiency might improve rapidly. We can look at recent efficiency changes to get a sense for how fast. GPT-4o mini is roughly 100x cheaper than GPT-4 and is perhaps roughly as capable all together (probably lower intelligence but better elicited). It was trained roughly 1.5 years later (GPT-4 was trained substantially before it was released) for ~20x efficiency improvement per year. This is selected for being a striking improvment and probably involves low hanging fruit, but AI R&D will be substantially accelerated in the future which probably more than cancels this out. Further, I expect that inference compute will be inefficent in the tail of high inference compute such that efficiency will be faster than this once the capability is reached. So we might expect that the number of AI human equivalents increases by >20x per year and potentially much faster if AI R&D is greatly accelerated (and compute doesn't bottleneck this). If progress is "just" 50x per year, then it would still take a year to get to millions of human equivalents based on my earlier estimate of 20k human equivalents. Note that once you have millions of human equivalents, you also have increased availability of generally substantially superhuman AI systems.