The Great Accretion and the Great Depression
Introduction
Few decades in modern economic history have been scrutinized like the 1920s and 1930s: a burst of prosperity and confidence followed by collapse on a scale that reshaped politics, policy, and the global economy. A recent line of research asks a deceptively simple question: did the very success of technological progress in the late 19th and early 20th centuries plant the seeds of the Great Depression? In a new macroeconomic modeling exercise, economists Harold L. Cole, Stefano Cravero, and Jeremy Greenwood argue that the United States may have suffered from a kind of “great accretion”—an overbuild of capital—driven by expectations formed in an era of extraordinary innovation, even as the pace of new, transformative products slowed and consumer demand became easier to satisfy. Their conclusion is not that technology caused the Depression outright, but that the dynamics of innovation and investment could have made the economy more vulnerable—and the downturn more severe—than standard accounts imply.
Historical context: the promise—and maturing—of the Second Industrial Revolution
The Second Industrial Revolution, stretching roughly from the late 19th century into the early 20th, introduced general-purpose technologies that reorganized production and daily life: electrification, the internal combustion engine, chemicals, telecommunications, and modern systems of mass production. By the 1920s, many of these technologies were diffusing rapidly. Electrified factories reconfigured industrial layouts; automobiles and trucks transformed transport and retail distribution; consumer durables—radios, refrigerators, vacuum cleaners—began moving from novelty to aspiration.
The “Roaring Twenties” in the United States combined real productivity gains with buoyant financial conditions and a powerful cultural narrative: modernity was accelerating, and with it, prosperity. Yet the decade also displayed a pattern common in technological revolutions: early breakthroughs give way to incremental refinements. The first wave of product innovation creates new markets; later, firms compete by improving processes, lowering costs, and scaling production. That is where the new work places emphasis: a shift from major new products to continuous process innovation may change the relationship between investment, demand, and macroeconomic stability.
Main analysis: how innovation can encourage overinvestment
The core idea is straightforward. Firms invest when they expect profitable future sales. In an economy that has recently experienced transformative product innovations, investors may extrapolate: tomorrow will bring new markets and expanding demand, justifying more factories, machines, and capacity. But if the flow of major new products slows—or if households’ demand for durables becomes “satiated” at the margin—then the economy can end up with too much installed capital relative to the revenue that capital can earn.
This is not merely a story about a stock market bubble, though the late-1920s equity boom and the October 1929 crash remain central to any narrative. It is instead a mechanism that links technology, expectations, and the composition of innovation to real investment decisions. Process innovation—better methods of producing existing goods—tends to raise productivity and lower unit costs. That sounds unambiguously good, but it can have a destabilizing side effect: if firms keep investing to chase efficiency gains while demand growth is flattening, competition can compress margins, leaving the economy with excess capacity and weaker returns on capital.
In a macroeconomic model that distinguishes product innovation (new goods that expand or reshape demand) from process innovation (cost-reducing improvements to making existing goods), the authors run proof-of-concept simulations showing that these forces can amplify downturn dynamics. Overaccumulation makes the economy fragile: when profits disappoint, investment can fall sharply; falling investment reduces incomes and demand, further worsening profitability—a feedback loop that macroeconomists would recognize as a propagation mechanism.
This perspective complements, rather than replaces, established explanations of the Great Depression. Monetary contraction and banking distress—dramatically intensified after 1929 and aggravated by waves of bank failures in the early 1930s—are widely seen as key drivers of the depth and persistence of the slump. The international gold standard transmitted deflationary pressures across countries and constrained policy responses. The novelty of the “great accretion” approach is to add another layer: structural investment vulnerability created during the boom years, rooted in the innovation cycle itself.
Importantly, this framework also speaks to a long-running puzzle: why did the downturn prove so severe relative to the initial shock? If the economy entered 1929 with a capital stock built for a world of continually expanding product frontiers, then a reassessment of growth prospects—whether triggered by financial panic, policy tightening, or global shocks—could force a painful adjustment. In that sense, technological optimism becomes a channel through which the 1920s set up the 1930s.
Conclusion: why it matters for economic history
The Great Depression remains the benchmark crisis because it fused finance, policy, technology, and social upheaval into one global event. The “great accretion” thesis matters because it reframes the 1920s not only as a story of speculative excess but also as a story of real economic structure—how the innovation process shapes investment, and how investment can outrun demand when a technological revolution matures.
For economic historians, the lesson is methodological as much as interpretive: to understand boom and bust, it may not be enough to track credit conditions and monetary policy alone. One must also ask what firms thought the future economy would look like—what kinds of innovations they expected, what markets those innovations would open, and whether the demand side could keep up. That interplay between technological waves and macroeconomic fragility is not confined to the interwar years, which is precisely why the debate remains so timely.