Cycles we read against

Ray Dalio long-term debt cycle (~50-75yr): sustained credit growth lifts debt-to-income ratios past the point short-cycle rate adjustments can resolve. Cycle climax = deleveraging phase, resolved via some mix of austerity, debt-restructuring, money-printing, and wealth-redistribution. Terminates with a new monetary order. Classical phases: new order → prosperity → excess → debt-peak → deleveraging (deflationary or inflationary or balanced) → new order.

Ray Dalio short-term debt cycle (~5-10yr): credit expansion drives above-trend output + rising inflation → central bank tightens → debt-service rises faster than income → asset-price contraction + recession → central bank eases → expansion restarts. Classical business-cycle mechanism; central-bank reaction function is primary modulator.

Perez's Techno-Economic Paradigm (TEP) frames approx 50-year great surges of development around a new general-purpose technology. Each surge has four phases: (1) IRRUPTION — new technology enters, old economy still dominant; (2) FRENZY — financial capital decouples from productive capital, bubble forms; (3) TURNING POINT — bubble crash forces institutional reset; (4) SYNERGY — new paradigm diffuses productively through re-regulated economy, 'golden age'. Then MATURITY and setup for next surge. Five observed surges since 1770s: Industrial Revolution; Steam & Railways; Steel & Heavy Engineering; Mass Production/Oil/Auto; ICT. A possible 6th surge (AI + biotech + energy transition) is debated.

A 2-4 year industry-scale capex cycle driven by lagged capacity response to demand shocks. Chip-makers see demand spike, commit to multi-year fab build-outs; by the time the fabs come online, demand has adjusted and the industry faces glut. Prices crash; capex halts; next shock catches the industry under-capacity and the cycle restarts. Observables: WSTS monthly billings (demand), WFE book-to-bill (capacity commitment lead indicator), memory-price indices (first to crash in oversupply). Overlaid on this: US-China export-control events discharge surface tension at the national-security grain boundary, extending certain capex cycles while suppressing others.

Turchin's Structural-Demographic Model (SDM) decomposes polity dynamics into two coupled rhythms: a secular 200-300y wave of state-building then state-decay, and a nested 50y instability wave inside each secular downturn. Drivers: elite overproduction (too many aspirants per elite slot), popular immiseration (median living standard decline), state fiscal distress. When all three stack, political-stress index spikes and the instability wave peaks (civil war, revolution, major regime shift, or state collapse). Seshat Databank N>=8 pre-industrial polities + US quantitatively tracked.

A youth bulge is a cohort of 15-29 year olds that constitutes >=20 pct of the total adult population (or >=25 pct in acute Heinsohn framing). When this cohort cannot be absorbed into the labor market, higher education, or elite positions, the result is elevated probability of political violence, revolution, civil war, or large-scale emigration. Mechanism: Goldstone emphasizes elite-political coupling (second-sons unable to inherit); Heinsohn emphasizes the demographic-density mechanism directly; Urdal 2006 cross-national regression N>=85 country-decades confirms a statistically significant relationship with civil conflict.

Strauss-Howe saeculum (~80-100yr) sequence of four turnings, each ~20yr, driven by generational-cohort succession through four archetypes (Prophet, Nomad, Hero, Artist). First Turning = High (post-crisis renewal; strong institutions, weak individualism). Second = Awakening (institutions attacked, individualism rises). Third = Unraveling (institutions decay, culture fragments). Fourth = Crisis (climactic institutional reset — great war, revolution, or regime rotation). Generational replacement sets the archetype dominant at each stage.

ENSO (El Nino-Southern Oscillation) is a 2-7 year coupled ocean-atmosphere oscillation in the tropical Pacific. Walker circulation + thermocline tilt swing between warm-east (El Nino) and warm-west (La Nina) states; ONI (Oceanic Nino Index) 3-month running SST anomaly in Nino 3.4 region crossing +/-0.5 C defines phases. Teleconnections drive hurricane seasons, droughts, grain-crop yields, and shifts in global atmospheric circulation.