The population of Spain in the 21st century: marked contrasts in how demography and geography have changed

Spain is one of the European countries in which demography has grown the most strongly over the first quarter of the 21st century, its population rising from over 40 to nearly 50 million. These figures however mask deep transformations. What are the characteristics underlying Spain’s population dynamic? What are the explanatory factors? What is the geography of the resulting population distribution?