For deme U, the population count was 9985 until a change 674.069 generations ago, where it changed to 2765, remaining steady thereafter.
time_units: generations
demes:
  - name: U
    start_time: .inf
    epochs:
      - start_size: 9985
        end_time: 674.069
      - start_size: 2765
        end_time: 0