Published 2026-10-14
Point-in-time data
Point-in-time data reflects what was actually known at each moment — as first reported, with the constituents of that day. It is the opposite of a dataset quietly restated with what we know now.
What it is
Point-in-time data reflects what was actually known at each moment — figures as first published, index membership as of that date, not as it stands today.
Why it is the fix for two biases at once
It is the concrete answer to both look-ahead bias and survivorship bias:
- A restated figure includes later corrections. A point-in-time figure is what a decision-maker saw.
- Today’s index members exclude the companies that failed. Point-in-time membership includes them.
A backtest run on restated data with today’s universe is testing a market that never existed.
How to check
Ask one question: is this the value as it was known then, or as it is known now? If the dataset cannot answer that, none of its results can be traced to a real decision.