Deme Z maintained a population of 7948 until there was a shift 9551.23 generations ago that reduced its numbers to 4855, a figure that has remained the same since.
time_units: generations
demes:
  - name: Z
    start_time: .inf
    epochs:
      - start_size: 7948
        end_time: 9551.23
      - start_size: 4855
        end_time: 0