Month by year seasonality
What it shows
The month × year heat map: each cell is the total price change in that month of that year, and the summary column is the month's average across all years in the window. Color encodes direction and strength (green = up, red = down). A month row only gets badges once it has enough observed years.
How to read it
Read row by row: a month is interesting only when the same color repeats across most years AND the average carries the significance badge. One strongly green year can inflate the mean, which is why the full year-by-year breakdown is shown, not just the average. A historical tendency, not a forecast.
Parameters
- Cell (month, year)
- The total % change in one month of one year: a single observation that proves nothing by itself.
- Month average
- The mean of the month's total changes across all years in the window (n_years = years with data). Only this column speaks about a tendency.
- FDR-significant
- The green badge: the result passed the multiple-comparison correction (Benjamini–Hochberg). Without it, with ~30 tests per profile, a few “significant” results are pure chance.
- Stable over time (walk-forward)
- The stability badge: the effect keeps the same direction in both the earlier and the later half of the window. “Unstable” = the tendency may have already faded.
Example
April shows +4%, +6% and +3% in three consecutive years with a significant +4.3% average, which means a consistent historical tendency. November with +18%, −9% and +2% has a positive mean, but the spread shows a single year produced the whole result.