Point-in-time is not enough

Update on the timing problem. The standard answer is point-in-time data, or an as-of join in a feature store. For every row, only use what was available at that time. I did that. It is necessary, but it does not solve the thing I wrote about in December.

An as-of join fixes each row. It does not tell you whether the cross section is complete. If 40% of the companies have reported and the other 60% are late because their news is bad, every single row is point-in-time correct and the signal is still wrong. So now I think about it as two different questions. Is this row available (per row), and is this snapshot complete enough (per cross section). Most tools only answer the first one.