As we discuss scaling in human societies, the question naturally arises of what factors will eventually limit growth.
Limits to Growth
The Limits to Growth (Meadows et al. (1972)) is the title of a famous 1972 report based on the World3 computer model of the Club of Rome. The model simulates the development and interplay of five factors: human population, food production, industrialization, pollution, and nonrenewable resource consumption.
Meadows et al. is well-known as one of the major early studies in computational ecology. However, the report has also gained notoriety for pessimistic and inaccurate forecasts. For example, Meadows et al. projected the expected lifetime of various nonrenewable resources, including metals and fossil fuels. The projections are based on three scenarios: a simple ratio of known, economic reserves to annual production (the R/P ratio), the R/P ratio with a projected annual growth rate in the usage of the resources, and the R/P ratio with projected annual growth rate with reserves multiplied by five. Many resources, including petroleum and natural gas, should have run out by 2024 under all three scenarios.
Meadows et al. is pessimistic about the capacity of new technology to address limits to growth. In their discussion of the subject, Meadows et al. address three barriers for technology to achieve sustainability. First, new technology must overcome the limitations on resource availability discussed above. Second, technology must control rising pollution, which the World3 model holds will threaten human civilization. Third, technology must increase yields in food production to feed a rising human population.
Several updates and analyses of The Limits to Growth have been published since 1972, including Herrington (2021). She finds that, relative to the most of the scenarios of The Limits to Growth, the world has shows greater reserves of non-renewable resources, most aligning with that paper’s “Business As Usual - 2” (BAU2) scenario. Considering a range of ecological metrics, she finds that BAU2 and CT–the Comprehensive Technology scenario which posits a higher than historical rate for technologies for pollution control, resource efficiency, and agricultural yields–best fit empirical data. Both scenarios posit a peak in world gross domestic product by the mid-21st century, though the decline from the peak is sharper under BAU2. Herrington posits that pollution, particularly greenhouse gas emissions and the resulting climate change, is the most immediate cause of collapse under BAU2.
Herrington (2021) suffers from a similar problem as the original The Limits to Growth and other similar studies in that it applies a limited role to new technology, despite technology being the major reason for deviation between the forecasts of The Limits to Growth and reality. She forecasts that under the CT scenario, the rate of technological improvement–necessary to extend resource availability, food production, and pollution control–will stagnate.
Peak Oil
“Peak oil” refers to an expected worldwide peak, followed by decline, in world oil production. Peak oil forecasts are based on the Hubbert peak, developed by the petroleum geologist M. King Huubert (Hubbert (1956)). Hubbert observed that fossil fuel production in a region, such as a state in the United States, tends to follow a normal curve, or a bell-shaped curve. Such a curve initially appears to be exponential, showing a certain percentage increase every year, but eventually shows a slowing growth rate, a peak, and then a decline.
Hubbert applied a best fit normal curve to oil and gas production in the United States and forecast that these two commodities should see peak production around, respectively, 1965 and 1975. According to Kriel (2024), the United States saw a peak in oil production in 1970 of 9.6 million barrels per day (mb/d) and a general decline to 5.0 mb/d in 2008, but then oil production rebounded with the deployment of hydraulic facturing and horizontal drilling, reaching a value of 12.9 mb/d in 2023.
A lesser-known aspect of Hubbert (1956) is the advocacy for nuclear power. Written at the dawn of the civilian nuclear industry, and at a time of great expectations for it, Hubbert observes that the energy content of then-known uranium reserves vastly exceeded that of fossil fuel reserves, and with population stabilization in the near future, nuclear power had the potential to power civilization at a high standard of living for millennia.
Potential Production of Fossil Fuels and Nuclear Power. Image from Hubbert (1956).
Hubbert’s forecast for United States oil production appeared to be fairly accurate for 50 years after the paper’s publication, but he too failed to foresee the eventual impact of oil production technology from the late 2000s. So far, he has also greatly overestimated the potential of nuclear power, but based on a 5000 year forecast window, the industry’s slow start in the first 70 years might be only a blip.
Internal Limits to Growth
Manfroni et al. (2013) situate their work in the context of limits to growth, but while most works in this genre focus on external limits–resource availability and pollution–this paper focuses on internal limits to growth, specifically on working hours.
Our World in Data documents that, in several wealthy countries, average working hours have generally fallen since the 19th century.
Working hours in select countries from 1870 to 2017. Image from Our World in Data.
Manfroni et al. cite Zipf (1941), who, working in the wake of the Great Depression, identifies the saturation of consumptive capacity as the operating limit to growth during that time. For economies to continue to grow, it is necessary for individuals to consume more, which in turns necessitates a greater amount of leisure time and thus fewer working hours.
Therein lies a paradox, according to Manfroni et al. Economic models, such as those based on the Solow-Swan growth model (see Solow (1956) and Swan (1956)), assign a prominent role to labor in economic growth. Thus according to Manfroni et al., more leisure is necessary to sustain the consumptive driver of growth, but this necessarily comes at the expense of working hours, which are necessary to sustain the productive driver of growth. This paradox is what Manfroni et al. identify as an internal limit to growth.
Manfroni et al. offers important insight about the role of working hours in economic growth, and its hypothesis serves as a plausible explanation for why economic growth has been slowing in many wealthy countries since the early 1970s, as documented by Cowen (2011). However, the work suffers from several significant shortcomings. The treatment of consumption as a driver of economic growth is superficial and does not engage with recent economic research on the subject. Like many Malthusian works, Manfroni et al. does not sufficiently account for the role of new technology. In particular, it does not assess the potential for technology to sustain economic growth despite a decline in working hours, even though this has been the case in the past.
References
Manfroni, M., Velasco-Fernández, R., Pérez-Sánchez, L., Bukkens, S.G., Giampietro, M. “The profile of time allocation in the metabolic pattern of society: An internal biophysical limit to economic growth”. Ecological Economics 190: 107183. December 2021.
Zipf, G.K. “National unity and disunity; the nation as a bio-social organism”. Principia Press. 1941.
Solow, R.M. “A contribution to the theory of economic growth”. The Quarterly Journal of Economics 70(1), pp. 65-94. February 1956.
Swan, T.W. “Economic Growth and Capital Accumulation”. Economic Record 32(2), pp. 334-361. November 1956.
Cowen, T. The Great Stagnation: How America Ate All The Low-Hanging Fruit of Modern History, Got Sick, and Will (Eventually) Feel Better. Dutton. January 2011.
Meadows, D. H., Meadows, D. L., Randers, J., Behrens, W. The Limits to Growth. The Club of Rome. 1972.
Herrington, G. “Update to limits to growth: Comparing the World3 model with empirical data”. Journal of Industrial Ecology 25(3), pp. 614-626. June 2021.
Hubbert, M. K. “Nuclear Energy and the Fossil Fuels”. Houston, TX: Shell Development Company, Exploration and Production Research Division. March 1956.
Kriel, E. “United States produces more crude oil than any country, ever”. United States Energy Information Administration. March 2024.