Sinusoidal History

Overview

Sinusoidal History puts ten long-wave theories of history on one shared timeline, 1600 to 2050: Ibn Khaldun, Kondratiev, Huntington, Schlesinger Jr., Carlota Perez, Peter Turchin (twice), Ray Dalio, Strauss-Howe and Modelski. Each is drawn as a simple wave from a documented period for the theory and one documented peak year, so you can see where they line up and where they disagree.

Nine of the ten sit beside a real long-run data series - political polarization, top-1% wealth share, war deaths, productivity, share of world GDP and more. Drag a cycle's peak year and watch its correlation with the data move. Each pairing also carries a test whose rules were fixed before any results, and the honest verdict today is that all nine records are too short to run it.

Nearly every curve peaks near the present. The site tells you why: that is a selection effect, not convergence - readers pick up these theorists because their climaxes land in our era. It compares theories. It does not forecast.

Why I built it

Mark R pitched it on a phone call, both of us out walking: could you plot Khaldun's stages, Huntington's 60-year cycles and the rest as actual sine waves on one axis and see where they net out? I told him I'd take a swing. What I wanted was a chart that stays honest - one knob per cycle, every peak year a choice I can defend, and a plain answer when the data can't settle it.

How it works

1. Open the chart - ten cycles on one 1600-2050 axis, one row each or overlaid together 2. Pick a cycle you've heard of - its page gives the period, the peak year and why that year was chosen 3. Set it against the data - see the paired series and the correlation, then drag the peak year and watch it change 4. Read the verdict - each pairing says whether its record covers the three full periods a test needs 5. Share what you see - the link keeps your view (tab, focused cycle, time range, calibration), and you can download a poster or embed a chart

Feature highlights

• Ten theories, one axis - Khaldun to Modelski, each drawn from a documented period for the theory and one documented peak year.
• Real data beside nine of them - long-run series, each with a provenance file that records its source and every transform.
• A peak-year slider - move a cycle's peak and watch its correlation with the data rise or fall.
• An honest verdict - a test with rules fixed before any results; today it says every record is too short to run it.
• A page for every cycle - period, peak year, the reasoning behind it, caveats and sources, at a link you can send.
• Share, print, embed - the link keeps your view (tab, focused cycle, time range, calibration), the poster downloads as a PNG, and a chart embeds in your own page.
• Open data and API - the CSVs and three JSON endpoints are free to use, with no key.
• Citable - a dated reading for each year from 2026 and an archived release with a DOI.

Pricing

Free. No account, nothing to buy.

Notes

• For whom: anyone who has heard Dalio, Strauss-Howe or Turchin quoted and wants to see how the claim sits against the record.
• Privacy: no accounts, and the site runs no analytics.
• Not advice: a comparison tool, not a forecast. Every cycle here is contested, and the peak year chosen for each is a judgment call.
• How it's built: open source - the code is MIT licensed, and each data series keeps its own source's license.