Suburbanization Processes in Sofia: Demographic, Socio-Economic and Spatial Transformation of the Agglomeration Area

The paper studies the agglomeration area of Bulgaria’s capital, Sofia. The territorial scope of the metropolitan agglomeration encompasses 7 (LAU 1) municipalities including Sofia, Bozhurishte, Elin Pelin, Gorna Malina, Kostinbrod, Slivnitsa and Svoge, and comprises 146 (LAU 2) individual settlements. The total area of Sofia agglomeration covers almost 3,550 km² (3.2% of national territory), while it had 1,359,270 inhabitants (almost 21% of national population) according to the last population census (7 September 2021). During the whole period between 2001 and 2021, Sofia agglomeration has grown in population by more than 95,000 people (7.6%). Bozhurishte, Kostinbrod and Elin Pelin, along with Sofia municipality itself, are the municipalities with the best demographic indicators within the agglomeration area. According to the typology of Webb, type 6 agglomeration settlements (migratory and natural decrease, natural > migratory) are predominant during the first subperiod (2001-2011), while type 8 (migratory increase compensates for natural decrease) has become the leading type in the second subperiod (2011-2021). Despite the increasing number of type 8 settlements, however, the population decline of Sofia city alone (19,361 people) exceeds more than twice the combined population growth of all type 8 settlements (8,929 people), and as a result – the total population number of the agglomeration declined during the second subperiod. In 2021, the GDP in Sofia agglomeration represented 43% of the national economy, while the GDP per capita in Sofia (BGN 38,891) was more than double of the national average. A significant number of the industrial sites are located in the neighbouring municipalities that fall within the agglomeration, with leading economic activities in manufacturing, transport and logistics. The distribution of FDI, however, is uneven: some 97% of them concentrated in Sofia municipality alone. Sofia agglomeration is distinguished by a relatively stable and balanced labour market, characterized by high economic activity and low unemployment rate compared to other agglomerations in the country. Together with the demographic processes, the increasing soil sealing is another evidence of the spatial expansion of suburbanization. The largest share of new soil sealing was observed in Sofia municipality itself (approximately 370 ha), followed by Elin Pelin (105 ha), Bozhurishte (46 ha) and Kostinbrod (32 ha). Based on the intensity of new constructions and population change, the so-called zone of active inbuence of the agglomeration core has been outlined. The zone is made up of settlements meeting two conditions: they have a high intensity of new constructions and they are type 8 or type 7 according to the typology of Webb in the period between 2011 and 2021. During the considered period, the northern, eastern, southern and western peripheries of the agglomeration area developed each in its own speciac way, with dieerent new construction intensity, morphological structure and inter-settlement spaces. Suburbanization processes observed in Sofia are generally comparable to those of other post-socialist European capitals in terms of historical legacies, demographic transformation, spatial dynamics, and land use shifts.