For deme Z, the population count was 9239 until a change 8986.391 generations ago, where it reduced to 1349, remaining steady thereafter.
time_units: generations
demes:
  - name: Z
    start_time: .inf
    epochs:
      - start_size: 9239
        end_time: 8986.391
      - start_size: 1349
        end_time: 0