Three of every four Catalan counties registered seasonal population increases in 2015, according to the Seasonal Population Estimates. The county with the highest seasonal population in absolute terms was El Tarragonès, with 53,531 people, the equivalent of annual full time equivalents (AFTE). It was followed by El Baix Empordà (32,022 persons AFTE) and La Selva (29,876 persons AFTE). At the other extreme, of the counties with seasonal population decreases we can highlight El Baix Llobregat (−26,202 persons AFTE) and El Vallès Occidental (−23,774 persons AFTE).
In relative terms, the top places in the chart are occupied by a group of mountainous counties led by La Cerdanya, L'Aran, El Pallars Sobirà and L'Alta Ribagorça.
Barcelona is the municipality which saw the largest increase in its seasonal population: from 64,757 persons AFTE in 2014 to 68,302 persons AFTE in 2015. It was followed by Sitges and Tarragona.
Of the 219 municipalities which provided results for 2015, 97 of them registered an increase in seasonal population. In absolute terms, besides Barcelona, (68,302 persons AFTE), which is the municipality in Catalonia with the largest seasonal population, Salou (23,928 persons AFTE) and Lloret de Mar (16,337 persons AFTE) are also worth noting. In relative terms, Santa Susanna stands out followed by Pals, Salou and Creixell.
The seasonal population estimates constitute an estimation of the population burdens supported by each municipality and measure the number of people there are in a municipality as a yearly average and a quarterly average. The calculation includes people that have some sort of association or relation with the municipality, whether that is because they reside there, work there, study there or despite not having their regular residence there, spend some period of time there (holidays, summer breaks, weekends, etc.), either in their own homes or in those of friends and family or in tourist establishments (hotels, campsites, apartments, etc.). Given the complexity of estimating non-obligatory movement involving no overnight stays, this has not been considered.
The measurement unit for seasonal population estimates are annual full time equivalents. Every day that a person is present in a municipality equates to 1/365 annual full time equivalents (AFTE). So, for example, a person who spends a week's holiday in a municipality equates to 0.02 AFTE.
The AFTE seasonal population or annual full time equivalent seasonal population is defined by the result of the balance between entries of population not resident in the municipality and exits of population resident in the municipality, measured as an annual average number of people per day.
AFTE seasonal population = AFTE non resident population present – AFTE resident population absent
Idescat published annually The seasonal population estimates are designed as a synthesised statistical activity that collects information from different sources, such as municipal population registers, population censuses, tourism statistics, employment statistics, education statistics, and statistics on the population's quality of life and habits.