No pico de sua população, Alexandria tinha pouco mais de 53 habitantes, conforme listado no página oficial da wikia . No entanto, pela minha matemática, há um restante (spoiler)
33 (give or take) residents after the events we have witnessed this season such as the attack by the Wolves and the break in by the walkers.
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Therefore, before the attack by the Wolves, the number should be around 51, seeing as though 2 residents (Pete and Reg) were killed before the Wolves and "The Herd" attack didn't occur until later in the season.
A incerteza vem do ponto "Vários outros residentes" na página da Wikia.