When There Are Too Many Men, or Too Many Women

Scarcity is the best marketer.

— Modern aphorism

The birth of a son can change a family budget twenty years before his wedding. In China, parents of boys in regions with a surplus of men began saving more: a future groom needed housing, a steady income and a position in a competition where there were more rivals than possible brides. Demography entered the bank account not as a government table, but as one more family buying an apartment for a son.

This example ruins the convenient habit of treating the sex ratio as background. Numbers do not merely change the probability of meeting someone. They change the incentives before the meeting: how much to study, earn and save; at what age to marry; how expensive a refusal is; which demands look realistic. Private taste stays private, but the price of a strategy is set by the number of people trying to make a similar choice.

Not the population at large, but the reachable pool

The phrase “there are fewer men” says almost nothing without the fine print. What matters is not the overall balance of the population but the local ratio of suitable and mutually available people: age, place, sexual orientation, education, the intention to enter a particular kind of union. A city may have more women, yet a shortage of men only in one age group; national statistics may show balance while migration has emptied a specific region. The relationship market turns out once again to be not one market but many partly overlapping rooms.

The scarcity of one side improves its outside options only when a potential choice can be turned into a real exit. Law, income, safety and social norms can block that possibility even when there are plenty of potential partners. A demographic shortage raises bargaining power not automatically, but through the availability of refusal.

A quasi-experiment from immigration lists

Joshua Angrist used differences in the sex composition of immigrant flows and the tendency of the second generation to form families within a close ethnic environment as a source of variation close to a quasi-experiment. Where there were relatively more men than women, women married more often, worked outside the home less often, and family incomes and men’s earnings were higher. The result is consistent with a change in women’s position on the marriage market, but it does not look like a simple story about emancipation: a more advantageous position came with a more traditional division of roles. The estimate applies to historical immigrant groups in which marriages were often made within one’s own ethnic environment, and it is not a universal coefficient for the modern dating market.

Bargaining power means the ability to get more of what you want, not an obligatory move toward a modern set of norms. If in a given environment a good outcome for a woman is tied to marriage, a husband’s income and the option not to work, a shortage of women can reinforce exactly that construction. The model does not choose the goal for the participant. It only shows whose consent has become more expensive.

Shang-Jin Wei and Xiaobo Zhang proposed a competitive saving mechanism for China. Their estimates linked the rising male surplus to higher savings, especially in families with sons, and interpreted this as an attempt to improve a son’s relative position on the marriage market. A single family may be acting sensibly: an apartment and savings really can widen a son’s choice. When many do the same, the general entry threshold rises, and one household’s advantage forces the neighbouring one to buy the same. The estimate applies to China during a period of rapid change in the sex ratio and depends on assumptions that allow a causal effect to be separated out; it does not prove that every family consciously formulated the motive that way.

This is a typical move from individually sensible behaviour to a collectively expensive result. In a similar way, a surplus on one side can increase investment in appearance, education, status goods or demonstrative reliability. Part of the spending creates real qualities; part only changes relative position. If all the candidates stand on tiptoe, nobody becomes taller than the rest, but everyone has to keep standing.

Scarcity fixes prices and norms

Australian colonization provided a historical quasi-experiment. In the eighteenth and nineteenth centuries, some districts received far more male convicts than female. In the places with the strongest male surplus, women married more often and worked outside the home less often. Later the demographic skew disappeared, while part of the more traditional views on women’s work persisted. The authors interpret this persistence as cultural transmission, though a historical design cannot fully rule out every long-run regional difference.

The mechanism requires no conscious conspiracy. Behaviour that pays off at a particular sex ratio turns into an expectation, then into a moral explanation and a family script. The next generation inherits not the original shortage but the norm that arose in response to it. This is how the geography of the past keeps working after people have forgotten the cause.

The number and the story about the number

Linking sex composition to behaviour statistically is easy; isolating the cause is hard. Regions with a surplus of men are often young, migratory, poor, on a frontier or growing fast. Crime, savings and marriage norms themselves affect migration. That is why the convincing comparisons are those where the composition changed for an external reason and competing explanations can be checked separately.

More convincing are studies where the skew arose for reasons relatively external to the subsequent behaviour: historical migration restrictions, the composition of arriving ships, birth policy or differences between immigrant generations. Even such quasi-experimental designs are not sterile. They narrow the set of explanations, but the result stays tied to particular institutions and a particular time.

An economic mechanism is tested by a chain. First, the numerical skew has to change the real availability of partners in the reachable pool. Then it has to change bargaining power or competition. Only after that should changes be expected in savings, housing, work, marriage or risk. If the intermediate links are not visible, a vivid story about demography may turn out to be a new version of national character.

The same standard is useful in personal observation. The phrase “it’s impossible to meet anyone in this city” may describe a real local shortage, but first you have to check age, goals, social networks and search channels. A national proportion is too coarse a map for the route to the nearest person.

In Chinese provincial data, a male surplus among young adults was associated with higher rates of violent and property crime. That is a strong result for a specific country and period, but not a universal law of male behaviour. A sex skew can intensify competition and risk-taking, yet its consequences depend on migration, the search pool, marriage norms, legal institutions and safety. The same numerical skew can produce different results in different systems.

At the level of an individual, the first task is to work out your own reachable pool of potential partners rather than repeat the national proportion. At the level of policy, it matters to see that a demographic intervention does not end with the number of births: it can change savings, housing, work, crime and norms for decades. Within a couple, an advantage created by a temporary shortage does not become a personal trait or a natural right. Scarcity can raise bargaining power when refusal is available, without raising anyone’s human worth.

Main sources

Angrist, J. D. (2002). How do sex ratios affect marriage and labor markets? Evidence from America’s second generation. Quarterly Journal of Economics, 117(3), 997–1038.

Wei, S.-J., & Zhang, X. (2011). The competitive saving motive: Evidence from rising sex ratios and savings rates in China. Journal of Political Economy, 119(3), 511–564.

Grosjean, P., & Khattar, R. (2019). It’s raining men! Hallelujah? The long-run consequences of male-biased sex ratios. Review of Economic Studies, 86(2), 723–754.

Edlund, L., Li, H., Yi, J., & Zhang, J. (2013). Sex ratios and crime: Evidence from China. Review of Economics and Statistics, 95(5), 1520–1534.