The roots of the phenomenon of mutuality stretch way back in time, emanating from associations of a religious character such as the confraternities or brotherhoods of medieval origin, and from the guild networks typical of the Old Regime. From the nineteenth century onwards, both in Europe and America, the old formulas of solidarity were expanded and reinvented in order to protect a large part of the population, mainly workers, from the uncertainty arising from the risks of sickness, death, industrial accidents or old age, in view of the passivity of the liberal state. It is difficult to determine common patterns of behaviour for this international phenomenon, which was conditioned by the political context and the growth rate of each country and by the diversity of the type and extent of coverage offered, and there is also a lack of statistics for some countries. Some basic common traits of the friendly societies, however, do exist. These include their limited capacity of coverage, especially the scant value and limited duration of benefits; the limited diversification of risk, as they were often dealing with workers of the same trade; the absence of actuarial techniques and extreme sensitivity to economic cycles due to the limited nature of their reserves. Generally speaking, their heyday was between the end of the nineteenth century and the beginning of the twentieth century.

Research on friendly societies in Spain has generated an enormous flow of publications in recent years.