The Great Divergence and a neglected variable: grain yield volatility as the missing dimension
The Great Divergence debate has generated two decades of productive argument, but I think both sides have been talking past a variable that might resolve the core puzzle. I've written a working paper that makes this case, and I'd welcome pushback from people who know this literature better than I do.
The puzzle that won't go away:
Pomeranz (2000) demonstrated that the Yangtze Delta and England were broadly comparable on many economic indicators as late as the eighteenth century. Allen (2009) argued that England's specific factor prices — high wages relative to cheap energy — created the incentive for mechanization. Huang (1985, 1990) documented "growth without development" in the Yangtze Delta: rising output through labor intensification, yet no transition to the factory system.
Each captures something real. But none answers the underlying question: why did the Yangtze Delta, with fertile soil, an extensive inland waterway network rivaling major European systems, a low disease burden, and the world's largest population, never develop the institutional and organizational preconditions for factory production? Pomeranz points to coal and colonies as England's lucky breaks. Allen points to factor prices. But what determined those factor prices in the first place? And why did the Yangtze Delta's abundant capital — well documented by Li Bozhong and others — never flow into fixed-cost industrial production?
The proposed answer: interannual grain yield volatility.
The continental East Asian monsoon imposed a level of harvest-to-harvest variability on Chinese agriculture that maritime northwestern Europe simply did not face. England's rainfall, moderated by Atlantic westerlies and the North Atlantic Drift, was remarkably stable year to year. The Yangtze Delta's output, driven by monsoon timing and intensity, fluctuated far more severely.
This volatility, I argue, is the variable that explains the institutional divergences both sides of the debate have documented but not fully accounted for:
Land tenure. England's rigid fixed-rent tenancy has long been celebrated as institutionally superior. But fixed rent appeared independently in China — the iron-rent of the Yangtze Delta, perpetual tenancy in certain localities. The legal form was the same. What differed was enforceability. Under recurrent monsoon shocks, rigid fixed rent was effectively unenforceable: harvest failure made tenants insolvent, and landlords had to grant abatements or face violent resistance. Fixed rent collapsed in practice into flexible risk-sharing — de facto sharecropping. In England, extreme harvest failures were rare enough that contracts could be enforced as written. The rigidity was not a superior invention but a dividend of climatic stability.
The Dujiangyan natural experiment sharpens this point. The irrigation system on the Chengdu Plain, built in the third century BC and still operational, virtually eliminated output volatility within its coverage zone. Inside that zone — same culture, same legal tradition, same political system — fixed rent became genuinely rigid, famine abatement clauses were absent or rarely invoked, and a wealthy class of managerial farmers emerged. Outside it, the standard monsoon-driven risk-sharing arrangements persisted. What changed across this boundary was not belief, not culture, not institutions — it was volatility.
Factor prices. Allen's high-wage economy in England was itself downstream of stability. Low volatility supported nuclear family structures and moderated population growth, keeping the labor force relatively scarce. In the Yangtze Delta, high volatility tied labor to the land (leaving meant risking starvation in lean years) and incentivized large families as self-insurance, producing chronic labor surplus that pushed wages to the subsistence floor. The factor-price incentive for mechanization was thus a consequence of volatility conditions, not an independent variable.
Huang's involution. The intensification of household labor that Huang documented was not a cultural preference but a rational adaptation. In a volatile environment, household production carried no rigid overhead and could retreat to self-sufficiency during downturns. The factory system, burdened by fixed costs (wages, rent, equipment, debt service), could not survive the recurrent demand collapses triggered by grain price spikes. Capital rationally avoided industrial investment — not because Chinese merchants were risk-averse or culturally conservative, but because the risk-adjusted returns were genuinely too low. Accumulated wealth flowed instead into land, short-term lending, or hoarding.
The California School's evidence problem. Skinner's influential model of Chinese market structure (1964–65) was built on fieldwork conducted on the Chengdu Plain — within the Dujiangyan stability zone. Pomeranz's and Wong's broader claims of market development comparable to England's drew primarily from the Yangtze Delta, where massive labor input had partially buffered volatility. Neither tradition engaged primarily with the North China Plain, where monsoon volatility was least buffered. When Huang examined the North China Plain directly, he found a qualitatively different economy: commercialization driven by fiscal pressure rather than voluntary specialization, combined with high self-sufficiency and acute household fragility. The scholarship that built the image of a highly commercialized traditional China drew its evidence disproportionately from regions where volatility had been most effectively suppressed.
The testable prediction:
The coefficient of variation of grain yields — calculable from modern climate data fed into low-input agronomic models — should predict land tenure form across pre-modern Eurasia. Regions below a threshold (preliminary indication: CV of roughly 12–20%) should exhibit rigid fixed-rent contracts; regions above it should exhibit sharecropping or flexible rent-abatement; regions near it should exhibit mixed arrangements. The table in the paper maps 21 regions across Eurasia against this prediction, and the correspondence is strong — but systematic empirical testing remains to be done.
Full paper (open access): The Economic Logic of China's Rise: Geography, Big Push, and the Engineered Invisible Hand
Full disclosure: I'm the author. I'd especially welcome challenges from people who work on Chinese agrarian history, European land tenure, or historical climatology. If this variable has already been systematically tested and I've missed the literature, I'd genuinely like to know.