Fertility and migration in the heart of the industrial revolution.

This study examines demographic growth and change in Tilleur in the valley of Meuse in Belgium during 1807-80 during the process of industrialization and urbanization. The proportion of immigrants (foreigners and Flemings) increased from 15% in 1807 to 65% in 1856. After 1856, population and industrial growth stabilized. During 1856-66 the proportion of natives stabilized, and the proportion of Flemings increased. It is argued that in Tilleur there were two phases: a foundation phase of industrial and population growth and a phase of maturation with decreased non-native population and greater similarity between groups. Immigrants contributed to the birth rate in greater proportions than their proportion in the population of Tilleur. During 1847-66 native population increased annually from 2.4% to 3.8%. Migrants' annual increases were diminished by the effects of mortality but expanded by the influence of in-migration. During 1857-66 the proportion of foreigners declined and marked the transition to a new phase. During 1830-66 the sex ratio grew from 93 to 119. During the Industrial Revolution in Tilleur, women shifted from outnumbering to undernumbering men. The iron and coal in the region attracted men. The sex ratio among the Flemish was 214 in 1866. In 1830 the proportion of fertile women was higher among immigrants and declined thereafter. Age at marriage rose for natives and declined for immigrants. The native population structure by sex, age, and marriage did not favor the birth rate. During 1866-80 the birth rate of foreign immigrants and rural natives declined, the birth rate of natives doubled, and the gap between these two groups narrowed. The changes among immigrants during the foundation phase led to fertility decline in the maturation phase. Marriage and migration interactions linked the industrial revolution with the demographic transition.