Until 919.96 generations ago, the population of deme U was 5540. At that point, it reduced to 596, where it has stayed up to now.
time_units: generations
demes:
  - name: U
    start_time: .inf
    epochs:
      - start_size: 5540
        end_time: 919.96
      - start_size: 596
        end_time: 0