During the first eight decades of the present century, the number of Spaniards doubled, from 18.6 million persons in 1900 to 37.6 millions according to the 1981 census. In other words, the net annual population expansion over this period was 0.88 per cent. Only during the 1920s, and again in the 1960s, did the average expansion for an entire decade exceed one per cent a year. Although this experience hardly constitutes a population explosion, Spanish demographers tend to speak of a demographic revolution. As Joaquín Arango argues, since at no stage in Spain's previous history had the population grown by more than 0.5 per cent annually for any length of time, the twentieth century presents us with a pronounced discontinuity in the long-term trend (Arango, 1987).

Evidence of a demographic revolution is furnished by a sharp fall in both the birth rate and the death rate throughout the twentieth century, shown in Table 1. The same source also testifies to two important short-lived developments against the prevailing tendency: the large number of deaths which resulted from the Spanish Civil War of 1936–9 and the upturn in the birth rate during the late 1960s and early 1970s, produced by Spain's belated ‘baby boom’. In addition, as Table 1 illustrates, the demise of the ultra conservative Franco regime and the appearance of a new morality associated with the resulting democracy, led to a dramatic decline in nuptiality.