A conclusion of the European Fertility Project in 1986 was that pretransition populations mostly displayed natural fertility, where parity-dependent birth control was absent. This conclusion has recently been challenged for England by new empirical results and has also been widely rejected by theorists of long-run economic growth, where pre-industrial fertility control is integral to most models. In this study, we use the accident of twin births to show that for three Western European–derived pre-industrial populations—namely, England (1730–1879), France (1670–1788), and Québec (1621–1835)—we find no evidence for parity-dependent control of marital fertility. If a twin was born in any of these populations, family size increased by 1 compared with families with a singleton birth at the same parity and mother age, with no reduction of subsequent fertility. Numbers of children surviving to age 14 also increased. Twin births also show no differential effect on fertility when they occurred at high parities; this finding is in contrast to populations where fertility is known to have been controlled by at least some families, such as in England, 1900–1949, where a twin birth increased average births per family by significantly less than 1.

中文翻译：

---

双胞胎支持在妊娠前人群中缺乏与胎次相关的生育力控制。

1986年欧洲生育计划的结论是，过渡前的人口大多表现出自然生育能力，缺乏依赖胎次的节育措施。英国的这一结论最近受到了新的实证结果的挑战，并且也被长期经济增长理论家广泛拒绝，其中工业化前的生育控制是大多数模型的组成部分。在这项研究中，我们利用双胞胎出生的事故来表明，对于三个来自西欧的前工业化人口——即英格兰（1730-1879）、法国（1670-1788）和魁北克（1621-1835）——我们没有发现证据表明婚姻生育力依赖于胎次控制。如果这些人群中的任何一个出生双胞胎，与相同胎次和母亲年龄的单胎家庭相比，家庭规模会增加1，而随后的生育率不会减少。存活到 14 岁的儿童人数也有所增加。当双胞胎出生的胎次较高时，对生育力也没有表现出差异性影响。这一发现与已知生育率至少由某些家庭控制的人群形成鲜明对比，例如在 1900 年至 1949 年的英格兰，双胞胎出生使每个家庭的平均出生率显着低于 1。