LLMs might accelerate alpha decay in trading
Here's how it works in a nutshell:
- free basic data
- conventional "top of mind" indicators and strategies - something LLMs know and trust because of multiple sources
- very similar backtest fitting
All of these combined lead to generating signals that use very similar logic. This crowding effect will cause 2 things: alpha decay and volatility spike. I'll expand on vol next time, alpha decay is a big enough topic
One recent paper in The Journal of Finance shows that anomaly returns are concentrated in the first month after information release and then decay soon after. In other words, even before LLMs, the monetization window for many signals was already narrow.
Now add LLMs to the research stack.
A 2025 paper on LLM-driven alpha mining makes the risk explicit: LLM-based approaches can rely too heavily on existing knowledge, generating homogeneous factors that worsen crowding and accelerate decay.
That is the part I think the market is underestimating. If many teams are drawing from overlapping public data, familiar factor logic, and similar backtesting workflows, LLMs help discover signals faster. But they also make it easier to produce the same kinds of signals faster.
My bet:
LLMs will not kill all alpha.
But they will compress the shelf life of copyable alpha.
So what can traders do about it?
Option A: accelerate strategies launch. Have a pipeline, be ready to halt underperformers. Expensive, time consuming, capital heavy
Option B: add alternative data, create/buy prop indicators, work on portfolio composition