Proto-industry, according to the theories, generated a growing supply of cheap labour which benefited European economic development at the cost of the labourers themselves. This growing labour supply is supposed to have been fuelled partly by free entry to proto-industry (e.g. from non-proto-industrial occupations and regions), a claim discussed above in Chapter 6, and partly by proto-industrial producers increasing their labour inputs even when demand fell, a claim discussed above in Chapter 7. Above all, however, labour supply is supposed to have increased because proto-industry caused population to grow unprecedentedly fast, regardless of economic trends.

In the mainly agrarian societies of pre-industrial Europe, the argument goes, marriage had to wait on inheritance of a farm or a craft workshop, and was regulated by landlords, communities and guilds. Consequently, people married relatively late (in their mid- to late twenties) and many poorer people never married at all. Sexual activity was permitted only to married couples, so controlling access to marriage also controlled fertility. Population growth was therefore minimal. Households were small because fertility was low and offspring left home young to become servants. Household structure was determined by the labour needs of the farm: kin complexity took the form of the ‘stem family’, and additional labour was provided by servants. There was a strong familial division of labour according to sex and age. Marriages and births followed the seasonal rhythms of the agricultural year.