Pretraining progress is mostly coming from data
How much of therapid progress in AI that we’ve seen over the last few years1 has come from data versus model improvements? The answer has big implications for the economics of frontier labs and the pace of future progress.
We investigate this question at a relatively small scale, and for pretraining specifically, from 2019 to 2025. During each of those years, a new open model recipe was published which codified that year’s publicly known algorithmic tweaks (for example, improvements in architecture, optimizer, initializations, learning rate schedule, hyperparams, etc). And during each of those years, there was also a new public data corpus (produced by broader scrapes and new curation/extraction/filtering techniques).
We train combinations of these year-representative model recipes and data corpuses across different scales of training compute (up to 1e19 FLOPs)2.
Obviously, we can’t compare these different models by their cross-entropy loss against a fixed dataset, since we’re varying the datasets they’re trained on. So instead we evaluate these models on end capabilities as measured by the OLMES eval (which aggregates 10 different relatively easy benchmarks, mostly multiple choice QA). Unfortunately, evaluating end capability rather than pretraining loss adds some noise to our results, as you’ll see in the graphs below, though we try to get cleaner bounds by running multiple seeds.
We find that from 2019 to 2025, 3.24x more compute efficiency gains have come from data improvements rather than model improvements (12.0x for data and 3.7x for models), at the 1e19 FLOPs compute budget3.
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Here is a grid which shows how much better a model we train does on the end capability we're testing it on, relative to the 2019 data + architecture baseline, at 3.16e18 FLOPs4.
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We find that the gains from data and model improvements are mostly independent and don’t interact (i.e. realizing the gains from some model improvement doesn’t require a specific training datapile, or vice versa). 88% of the variance in the OLMES score can be explained by additive effects of the model and data improvements (using a linear model).
Discussion
For context, let’s briefly summarize what changed on both the data and the model side from 2019 to 2025.
On the model side, we went from GPT-2 to OLMo-2, including key innovations in optimizers, positional encodings, normalization, activation functions, initializations, and more5.
On the data side, we started with OpenWebText in 2019, which contained just web pages linked from Reddit with enough upvotes and then deduplicated and filtered, and thus amounted to only ~9B tokens (this was mostly what GPT-2 was trained on). By 2025, open source data corpuses like UltraFineWeb not only are far larger (by using scrapes of the whole Internet), but also use much more sophisticated filtering (for example, by training a classifier to predict what data will empirically improve model performance).
A naive interpretation of our result is that most of the AI progress from 2019-2024 (the era of pretraining) was just better data engineering (extraction, curation, etc.), and that all the model work during that period was much less important.
But this is probab
