The islands of Ibiza and Formentera has quadruplicated their population in the last 160 years, according to the data done by the National Institute of Estadi'stica (INE). The growth of the number of homes has been much more spectacular, but the biggest changes has been from halves of XX century, with the tourist boom, since there has been a tendency to the loss in the number of children of the families. The fact that the population has grown more although the families have less children because the increase of the immigration produced the result of the tourist phenomenon, in which the islands happen to be lacking manual labor towards other regions or foreigners, there for has been receiving workers of services, Spanish as as much foreign.

The tourism also has caused the increase of European population that has established itself in the islands as a second residence or his first in the case of older people and this phenomenon also affects the population data. The city of Ibiza and municipioo of Sant Antoni have had a uninterupted growth during the studied period. First it had 5,118 inhabitants in 1842 and 34.826 in 2001, and the second it has happened from 3,539 to 15,081 in the same dates. Santa Eulària, Sant Josep and Formentera has had some oscillation and has gotten to register censuses lower than the previous one, but in the last years have experienced a remarkable ascent.

Thus, in 2001 Santa Eulària (second municipality in population) it had a census of 19,808 inhabitants; Sant Josep, of 14,267, and Formentera of 5.553. In the smaller Pitiusa, perhaps by its territorial limitations, the growth less is accelerated and exists a tendency to the comparison in number of inhabitants between the secondary municipalities of the island of Eivissa (Santa Eulària, Sant Antoni and Sant Josep). Sant Joan, atypical case the smaller growth, where in 1842 the census was of 3,655 inhabitants and in 2001, of 100 people less, that is to say, 3.555. But they had doubled the homes, since the 613 of 1842 happened to the 1,198 of 1991. The global numbers of Ibiza and Formentera have been increasing throughout all the exposed period. The number of the homes is significant to this ascending curve. The 4,062 addresses of 1842 have become 33.014 in the last.