Alphabet Seasonality: A Historical Window, Tested More Carefully

This case study uses adjusted daily GOOGL prices and completed calendar years from 2010 through 2025. The current year is excluded from every statistic.

Method before result

A disclosed algorithm scans fixed calendar windows only on 2010–2021 data. The 2022–2025 period remains untouched until after selection, so the later result cannot influence the chosen window.

What the data shows

The selected window is July 1–October 29 (120 days). The independent sample had a positive average but a negative median, an example of why an outlier can make a single average misleading.

Alphabet: average and median tell different stories

Alphabet provides the clearest warning against quoting only an average. The independent sample averaged +9.9%, but its median was -2.5%. One unusually strong year lifted the mean while the typical later outcome was weaker.

For an advertising-led business, shifts in digital ad spending, search competition, AI investment, and earnings reactions can matter more than any calendar label. The distribution is the insight here, not the average.

Independent check

The interactive chart separates annual open, high, low, and close outcomes. Review the held-out years as carefully as the historical selection period; a strong average does not make the next outcome predictable.

Research takeaway

This is historical context for Alphabet, not a recommendation. Explore GOOGL seasonality, use Ticker Analysis, and read How to Read Backtests before relying on a headline statistic.