Main article Bilbao .
As surprising as it may seem, demographic behaviour is one of the most direct and sensitive barometers the private experience of individuals and structural changes in a society. In this sense, demographic indicators represent a reflection of the processes of expansion and crisis that a community experiences as a consequence of any social, economic or political change that occurs within it. Most of the time, any demographic data, due to its ease of access, is quicker to use and to represent and synthesize any social state that occurs than the more problematic sociological and even economic data.
In this chapter we will try to take a look at the history of the population of Bilbao in contemporary times. As is logical to assume, during these two hundred years until today, the changes that have occurred in this town have been of enormous magnitude, in such a way that we will see how a small port and commercial city has been transformed into a large industrial and modern city, ending with the one we live in today: an even more modern city but projected towards the future thanks to enormous changes in its vocation and productive structure. If we are to summarize all the events experienced by the city of Bilbao during these two centuries, there is no doubt that two words would fit to adequately define it: transformation and adaptation to the new situations that it has had to live through.
From the point of view of demographic history, we will describe and analyse the way in which economic, social, political and cultural events affect and shape what we usually call the specific and particular "demographic " that corresponds to each stage that Bilbao has gone through. With this we want to express that each type of society, this term understood in a broad sense, corresponds to a different combination of demographic variables (nuptiality, fertility, mortality or migrations), which gives rise to a special demographic that acquires all its meaning when we observe it in conjunction with the socio-economic that produces it and at the same time gives it meaning and entity. It is for this reason that this chapter has been divided into four large sections that correspond to the major socio-economic stages that this town of Bilbao has gone through up to the present time.