Urban Development in Sierra Leone 12 indicators covering urban development for Sierra Leone. IndicatorLatest Year10-yr change Rank Population in the largest city 34.3% 2025 down 5.8% 62nd Population density 117.21 people per sq. km of land area 2023 up 26.0% 91st PM2.5 air pollution, mean annual exposure 22.46 micrograms per cubic meter 2023 up 8.7% 69th Population in urban agglomerations of more than 1 million 1.39 million 2025 up 33.0% 110th Population in urban agglomerations of more than 1 million, per capita 0.1573 units per person 2025 up 6.1% 88th Population in urban agglomerations of more than 1 million, annual 2.95 % change on previous year 2025 up 2.6% 33rd Population in urban agglomerations of more than 1 million, per unit 0.0002 units per US$ of GDP 2025 up 21.0% 8th Population in urban agglomerations of more than 1 million, per square 18.14 units per square kilometre 2023 up 32.8% 58th Population in largest city 1.39 million 2025 up 33.0% 109th Africa's Development Dynamics (AfDD) Table 23 - Ecological 25.86 Hectares 2020 up 44.4% 113th PM2.5 air pollution, population exposed to levels exceeding WHO 100.0% 2017 unchanged 1st Dollar value of all resources made available to strengthen 4.25 million 2023 up 14.8% 53rd