The migration boom coincided in time with the expansion in construction that took place in Spain between the years 1997 and 2007. Newcomers to the peripheral areas of the cities numbered 500,000 natives (85.47%) and 85,000 immigrants (14.52%), figures practically proportional to the percentages of both population types across the whole of Spain. This distribution prevented the proliferation of new ghettos in the cities.
Urban lands that were uninhabited in 2001 went on to house, seven years later, the dwellings of 234,000 natives (83.87%) and 45,000 immigrants (16.12%), almost half of these in Madrid. Some 19% of the neighbourhoods grew by more than double in the period under study, with the influx of 1.5 million people, some 6% of the Spanish metropolitan population.
In metropolitan areas that grow rapidly, it is interesting to study the migratory phenomenon taking into account urban growth. Without evaluating this factor, research studies have traditionally overestimated the rate of change of residence among natives due to the arrival of immigrants and, therefore, their displacement and the formation of ghettos.

The two main Spanish metropolitan areas showed a similar behaviour in the evolution of the population’s distribution between 2001 and 2008. As reflected in the graphics, in Madrid and Barcelona alike, the Spanish-born population increased in absolute values in the peripheral areas, mostly new neighbourhoods created as a result of the property boom. In contrast, the number of natives in capital centres decreased. Immigration grew above average in the more central areas. The red colour on the maps reflects a higher-than-average immigrants growth threshold. However, it must be taken into account that a significant number of immigrants also took up residence in the outskirts, which neutralised the overall segregation.