What was the population of the Byzantine Empire?

The Byzantine Empire experienced significant fluctuations in population from its inception to its collapse. It began with 18 million under Christian rule, peaked at 12 million by 1025 AD, and faced drastic declines due to plagues and invasions, dropping to around 50,000 by Constantinople's fall in 1453. The empire's resilience and ability to adapt amidst various challenges shaped its demographic shifts, reflecting cultural and external pressures throughout its history.