Until 4548.4449 generations ago, the population of deme Z was 9970. At that point, it changed to 2924, where it has stayed up to now.
time_units: generations
demes:
  - name: Z
    start_time: .inf
    epochs:
      - start_size: 9970
        end_time: 4548.4449
      - start_size: 2924
        end_time: 0